I'd also like to remind us of our discussion about roles in the first Concept Assessment where we decided that offensive routes generally seemed best for mons with middling stats:
What kinds of roles can Fire/Fairy reasonably fill? What kinds of roles does Fire/Fairy naturally lend itself to? What kinds of roles would be best for Fire/Fairy?
These questions might sound the same, but they're quite different. The first question asks in other words what our full design space is/if there are any roles that simply don't make sense. The second question is geared towards the inherent merits/demerits of the typing itself. Note that when looking at offensive merit, our super-effective coverage by the numbers isn't the only important factor: what STAB options this typing has access to, whether or not the mons that we hit SE can threaten us back, etc, are things to consider as well. Likewise, when looking at defensive merit, some of the mons whose STABs we resist may be able to beat us with coverage or utility options. The last question asks you to consider whether or not to lean into our natural strengths. For example, if we think our typing is geared towards defense, is it best to double down as a wall? Or is it best to shore up our offensive shortcomings, striking some kind of offense/defense balance as a tank or bulky wallbreaker?
Something to chew on since I think we've considered a lot of roles themselves in a vacuum with what Fire/Fairy can give us, and maybe a little less on what it can do in conjunction with an average spread of stats and the general aspects each individual typing can bring to the table.
Beyond Clefable, who has been essentially a metagame staple in previous generations despite its average stats, there have been very few vialbe Fairy types that didn't use their secondary typing to account for their average stats (i.e. the tapus are really good and have REALLY good stats, so I'll be ignoring them here). Klefki in particular stands out as it was a present enough threat in ORAS UU because of its additional Steel type (an inherently defensive typing), its ability Prankster, and it's broad movepool full of status moves. Similarly in ORAS, Azumarill made use of its Water typing (a very reasonable typing for both offense and Defensive capabilities), physical Water type attacking movepool and its absolutely life-saving ability in Huge Power to be successful. fairy types are able to cover up average stats in both offensive and defensive ways as shown by these two Pokemon (and sometimes at the same time as shown by Clefable).
Fire types, on the other hand, have almost always have had some kind of inherent offensive-ness that has allowed them to be fundamentally successful, as defensive Fire type Pokemon with average stats have rarely seen success in the top metagames. It wasn't until Gen 8 that we were able to see Fire type be able to take on a truly exclusively defensive niche (Ho-Oh in Gen 8 Ubers, and now Skeledirge in this gen), save for Heatran which was only afforded a specially defensive niche thanks to, again, the Steel type and REALLY GOOD STATS. Consider instead, a Pokemon like Torkoal that had very good defensive stats, but anguished in PU until obtaining Drought due to the rest of its features lacking any meaningful threatening presences whatsoever (ability and movepool, mainly). Considering viable fire types with more average stats not afforded a clearance by Heavy Duty Boots, we can find MAYBE Talonflame in early XY and ORAS which was viable thanks to its exceptionally good ability in Gale Wings which provided it a fundamental offensive niche, or Blaziken in current generations which has Speed Boost to supplant an otherwise middling 80 Speed. The point I'm hoping to make here is that, historically, Fire types are viable when they have a much more offensive presence, even without Heavy Duty Boots.
Should we want to take on an exclusively defensive approach to CAP32, by forcing it into a defensive pivot, wall, or boost remover, I fail to see how we will be reasonably successful with these locked-in typing and stats. Because we have opted for the Fire type, in order to have almost any defensive presence with our average stats, we will be locked into using some very specific items, and would likely need to bolster this mon significantly with a very wide movepool and very strong ability, and even then it would still be competing with Skeledirge and Arghonaut, both who can pull off the Fairy type better thanks to Terastalization, with the former also having Fire Coverage as a result. Furthermore, we are still substantially threatened by more defensive Pokemon STABS like Garganacl's Salt Cure, Venomicon's Sludge Bomb, and Snaelstrom's Razor Shell, which to me doesn't feel very good when the point of the mon is to maintain a defensive presence. Yes, Fire Fairy does grant an immunity to Dragon type moves, but beyond a Walking Wake or Dragapult Draco Meteor, or a Baxcalibur's Glaive Rush, are therethat many Pokemon actually spamming Dragon type moves? Even Hydreigon still threatens a defensive, more passive, Fire / Fairy type Pokemon, with its Earth Power if the Fire / Fairy type can't do much back to it (especially if it goes Tera Poison, for example).
Also with respect to Hazards, I think it would be a fools errand to try and make a Fire / Fairy typed mon one's primary means of setting or clearing hazards. The former is something that in theory could be done through careful tailoring of stats and moves, but even then, I fail to see why I would want to use this mon as a Rocks setter over Venomicon, Great Tusk or Crucibelle, and a Spikes setter over Arghonaut or Astrolotl, beyond threatening Corviknight and Equilibra (the latter of which still can beat us with its STAB). The latter is an even worse idea in my opinion. I recall a little while back on a team tour when building, I got some good advice that I think directly applies here: "You don't want your primary means of hazard control to be weak to hazards". Corviknight makes for an excellent Defogger for its neutrality to rocks and its immunity to Spikes without requiring any kind of an item (i.e. based solely on its typing). Tornadus-T was able to get away with running Defog and taking Stealth Rock damage because of its ability in Regenerator, and then later the introduction of Heavy Duty boots. Compare, then something like Moltres, who, like Tornadus-T, benefits from Heavy Duty Boots, which allows it to have a defensive presence. Despite it having the move in its movepool, Moltres never ran Defog consistently due to the fact that if it lost Heavy Duty Boots, it was crippled by its typing (Fire/Flying) and wouldn't be able to consistently return to the field of play. When we look at CAP32 then, after immediately looking at Moltres, while Fire / fairy won't take 50% from Rocks, it WILL take Spikes damage in addition to Rocks damage without Heavy Duty Boots, making it almost just as short-lived as a boots-less Moltres, which in my opinion makes it a poor candidate for a hazard remover without significant boons in later stages.
In comparison, when we consider Fire and Fairy together, suddenly we have two typings that both have demonstrated a clear offensive presence in the metagame, as they have excellent coverage, being resisted only by other Fire types. There are easily spammble moves from both typings on both sides of the physical / special spectrum, which means that this typing allows us to explore just how much a reasonably good typing and middling stats affects our "Power Budget" as listed in the questions section. I have to agree with a lot of the posters here who argue that we should take an
Offensive approach, ideally either an Offensive Wallbreaker, or Offensive Pivot . The combination of Fire/Fairy applies immense offensive pressure simply from these two provided STABs, and even if we were to take a more defensive route, odds are that through the process we will still be leaning on the offensive boons provided by this typing as
snake_rattler noted.
Of course, the Offensive presence will have to compete with the likes of Iron Moth, Cinderace, and Volcarona, but I think that there's still a clearly defined niche for a Fire/Fairy type: the ability to take on Arghonaut and Dragon types. As Brambane noted, Argh and Dragon types are able to more or less stop all of these previously listed Fire types dead in their tracks as they would have to handle not only these mons' initial types, but also any potential terastalizations. In contrast, CAP32 will be able to immediately threaten these mons due to STABs alone which is crucial when we consider the question "why run CAP32, when you could run another Fire type?" Furthermore, an offensively-leaning role allows us explicitly force switches with these more passive defensive Pokemon. I return to Arghonaut (because holy moly Arghonaut is a good mon) because Arghonaut presently rarely runs any water coverage, opting instead for its tried-and-true set of Knock / Spikes / Recover / Circle Throw. Arghonaut cannot immediately pressure a Fire / Fairy mon beyond Knocking Off its item as is immediately threated by potential Fairy STAB. There is a clear offensive niche for a Fire / Fairy type in this metagame, even one that has more average stats.
TL;DR I'm just repeating what's been said by the champions of an
Offensive Role for CAP32. I'm partial to one that has some kind of inherent power to be a nice strong
Offensive Wallbreaker, Offensive Pivot or even a
Glass Cannon.