First off, Toxicroak doesn't do very much to Metagross, Azelf, Infenape, and Jirachi, the top 4 OU leads in February.
For Flygon, Fire Punch seems a bit redundant, as Earthquake covers most steels anyways, barring Skarmory and Bronzong. You'll quite possibly be locked into Earthquake or Outrage anyways. Stone Edge would work better.
Alakazam is almost always out-performed by Gengar. But at the moment, neither are seen as often as they were with Bullet Punch Scizor running everywhere.
If you messed with your Metagross set a bit, you could easily make him your lead. Explosion and Earthquake/Meteor Mash over Thunder Punch and Ice Punch. I run mine with Occa Berry, to better take on lead Infernape, Azelf, Heatran, etc. and with 252 HP/236 Atk/12 Def/8 Spd. Lum Berry is also an option for Bronzong, Roserade, Gengar, and Yanmega leads as well. There is also the ever-present Leftovers at your disposal as well.
I would probably go with Rotom-H if you're looking for a tanking Scizor counter. It has Will-O-Wisp, Overheat, and resists Bullet Punch, Superpower, U-turn, but is weak to Pursuit, so keep that in mind.
Umbreon's moonlight is not as good as you think. With Sandstorm, it only recovers 33% and with all the Hippowdon and Tyranitar (esp. now that Latias is OU), Sandstorm is prevelant. So, go with wish, and quite possibly protect for scouting. There are much better walling options than Umbreon, though. Blissey or Skarmory wall much better than Umbreon, have better defenses, and have much more reliable recovery.
I hope that helps. I would help with synergy and such but am not to good with that aspect. So, hopefully someone else could do that.