Oh, incidentally, make sure you have a way to quickly strip the flesh from corpses. You don't want to get stuck with a bunch of zombies because you didn't have time to skeletonize them. If you can talk your DM into letting you use acid splash on dead creatures, that's a good one.
I have always been under the impression - maybe due to some flavor text of previous editions - that when you choose to make a skeleton out of a corpse it automatically just drops all the non-bone parts off and is a skeleton. But the reading of the current spell certainly does not imply that. I'd have to say, of all the abuses associated with this spell, that seems like a minor one.
2.) The Inspiring Leader feat scales really well for necromancers
Doesn't Inspiring Leader have a limited number of targets it can grant its temp HP to?
Yes; it only works on 6 creatures. Not sure if that would justify the otherwise-dump-stat 13 Cha requirement, plus your precious level 12 feat. Two 4th level castings of
aid by a cleric / paladin is better (although also a bit costly). Or just convince the bard to take it and include your underlings? But it
is a nice feat; level 13 + 13 Cha = 14 x 6 = 84 extra hit points every single short rest (if you have 6 targets).
3) Chain mail is definitely a good idea, although it can get heavy. But sticking them all in a bag of holding is a good plan to fix that.
5) Demiplane is only a 30x30' cube. That's 36 skeletons unless you could get them to squeeze together somehow (or stand on top of each other, which seems precarious). Also there's the question of how you'd get more in when the "control duration" of the current occupants had run out.

Still, it's a neat idea for transporting them around. If you could cast it through a scry (which the rules are murky about) that would be even funnier.
6) The bag of chickens would definitely fail the "bag of rats" rule.
7)
Planar binding is definitely a popular one (in theory, anyway) for getting concentration spells on your powerful summons.
9)
Create undead seemed pretty lackluster to me when I gave it a look months ago. You're just not getting much bang for the buck relative to what your same-level castings of
animate dead can do. Maybe I'm missing something.
Wind Walk is a druid spell.
Oops, I didn't realize wizards didn't have access to this. Man, I hate how spells are organized in the PHB...