Thoughts:
WreckDra's Team: Pretty good team; however it has a pretty gnarly Ho-Oh weakness that can't be ignored, it can come in on half the team and kill something. Given that this Pokemon checks Shaymin-S that's rather concerning. Most other things look covered.
malefic's Team: Also pretty good. I don't know if I would run Healing Wish Skymin on this team, you have no real sweepers to take advantage of it and you have Aromatherapy support already for Kangaskhan. I think the biggest issue with this team (aside from Electric Arceus weakness) is that this team doesn't really take full advantage of Skymin's unique qualities and is instead accentuating your team's weakness to Electrics, but you already said its hard to fit Skymin (which is true).
Mega-Swampert's Team: Using Skymin on stall is a neat idea but I think SubSeed works better since Leech Seed is nice for team support and the stally nature of the set fits the motif. You have an extremely reliable Ground check in Gliscor already and Skymin isn't all that strong of a Scarfer so I think that you could run something else in that spot. It also seems like you rely too much on your own Kyogre to check enemy Kyogre which is concerning. This team also gets wrecked by Electric Arceus, which Skymin isn't helping much against. I don't think it's a bad team, but I don't think it really makes good use of Skymin.
Level 56's Team: Mega Gengar and Gothitelle destroy this team. It's decent otherwise, but because its stall that's kind of a fatal flaw.
Worthlessnoob's Team: Really weak to Steels. Lack of Defog means Ferro and Keys can easily get 3 layers of Spikes which seriously hampers your core, and Heatran walls half of your team (though Skymin can act as a lure). You also acknowledged the Genesect weakness which is pretty severe. Running Skymin and Arceus-Grass together seems kind of redundant to be honest, you could try making Arceus into a Water-type or using Palkia + a different Arceus. Healing Wish to Stalltwo is cute though and VoltTurn to get Skymin in is a nice idea too.
orch's team: The concept of this team is cool. I think a bulkier Landorus-T set might have been preferred because Choice Band Ho-Oh can kinda just spam Brave Bird and smash up everything, and it gets free switches on Klefki and Arceus-Ghost, but you need the power to beat Xerneas after para. Arceus-Electric can come in after one layer of TSpikes go up and basically 6-0 with your only line of defense being a CM war with your own Arceus. U-turn Yveltal + Gengar teams are also problematic.
ApplepieFTW's Team: Fire-types wreck this team. Ho-Oh, Blaziken, Victini, and Heatran are all giant threats. For a team based around Skymin, that's not a weakness you can afford to have. :[
Something I saw as a common theme was that many of these teams don't do enough to address Skymin's problems with Fires and Electrics which might be why it's underwhelming some of you people. It is a hard mon to teambuild with though. Just my 2 cents.
Voting for orch as I think the team and its concept are pretty cool.