Hey, my friends and I started a Draft League that is now in its ninth season. Since we didn't have the expertise back then to set up our own point system, we designed our own rules for picking, which were based on the Smogon Tiers.
Long story short:
For the first time, we're introducing the rule that a Pokémon from the NU tier can terastallize, but limited to one Same Type Tera and two other types.
What would you say are the best Pokémon from NU for this?
Draft league functions a tad differently than a standard NU battle, and I should preface that certain Tera types here might not always be applicable to that environment.
That being said, in my opinion, there are a few Pokemon that are great Tera captains (so to speak) and utilize Tera quite well
- Eelektross has a diverse movepool and solid stats to back it up. Currently in the NU metagame, its common Tera types are Poison, Fairy, and Steel, which all provide unique defensive profiles coupled with its Levitate ability. You really can't go wrong with any solid typing for the Pokemon (outside of like, Tera Bug I guess).
- Dudunsparce is a phenomenal Tera Pokemon for similar reasons to Eelektross- great stats, solid movepool, and a diverse set of roles. For Tera types on this Pokemon, you (again) can't really go wrong. In the NU metagame in particular, Tera Ghost, Poison, and Fairy are all solid choices, but in draft league I think Tera Water or Flying could be good defensive choices as well (Flying also gives you STAB on Air Slash for ParaFlinch shenanigans).
- Another Pokemon I like with Tera is Rotom (in its base form). Rotom is a unique fella that utilizes a high number of sets in NU (utility with Will-O-Wisp, Choice Scarf, Nasty Plot) and performs even better with Tera. Like Eelektross, it has Levitate, and can utilize self tera types (Electric and Ghost) quite well, in addition to Fairy, Steel, and Fighting (to a certain extent at least).
- A fourth Pokemon I like with Tera is Jolteon. With Electric types in general, they benefit quite a lot with tera. Jolteon is slightly one dimensional, but Calm Mind sets with Tera Ice, Ghost, or Normal (while running Hyper Voice) are all quite nice. By extension, you could also run Grass or Water
- Scyther is a Pokemon that can utilize many different Tera types to great success. With its high attack and speed and access to Swords Dance, it can punch holes or become a nuisance with Tera Grass coupled with Technician Trailblaze. Flying is a fine type as well, giving you a much stronger Aerial Ace. Tera Ground is nice as well to avoid Electric and Rock moves too.
I hope this guides you in the right direction! If you have any additional questions on the topic, feel free to ask in the NU room on Pokemon Showdown!, or view the SmogDex analyses written by community members for the Pokemon in the tier for more information :)
stays in NU, Beartic 
stays in PU/ZU;
