is there anything stopping the Good-aligned 'Necromancer'?
There shouldn’t really be one anyway.
Is there anything stopping you using Animate Objects, with or without Permanency, to affect a bunch of corpses? If so, what? And would that qualify as an Evil, Chaotic, or Neutral act?
Corpses are officially objects, so this seems (oddly enough) legit. The animate objects spell isn’t inherently Evil like animate dead, nor will your animated corpse involve a soul forcibly bound to it or whatever it is that makes animate dead evil in the first place. Depending on your setting, desecrating a corpse may be considered Evil or un-Lawful.
Have you ever heard of this being done?
No, I have not.