I didn't see that your groudon/kyogre question was sarcastic lol. Now I feel stupid for answering it.
Np. (<at the sarcasm thing)
Yes it will work just doing it on TransN and not YRotN or XRotN. I haven't tested it myself but it should be fine. Also, sorry I forgot to answer that, it is actually better to invert first if you are making custom animations, because you will make them the way they are supposed to look in the first place so there will be nothing to swtich around. The only thing you have to remember though is that the right and left bones are switched and I tend to forget a and grab the wrong arm/leg lol.
But would it still be fine if I made the custom animation first? Like make the animation the way I would like with the improper hand. Then invert it so it becomes proper. Would that not still work?
There'd probably be some minor things that would need changing after inverting though. Plus, it would personally feel weird to work with flipped textures.
Then again, whatever makes things easier.