To be frank most of the time I'd rather the enemy don't have buffs than I have them.
What use is to mirror, say, unflinching, when you can't do anything with it, because the problem is enemy can BB you mid combo, and having your own unflinching doesn't help. The only buff I'd really like to mirror would be enrage probably.
It's like strictly inferior doublicious. So I'd rather have doublicious. Not to mention this SA pretty much locks you out of chaos.
Well, I guess gaining precision stacks is sort of okay, but there aren't many buffs that expire at a useful rate to reliably feed precision. RE, HM and Grudge armour stacks come to mind, but doing RE without chaos or buff removal is suicide even with an occasional precision (remember, precision will not trigger his SA so he would not gain armour stack so you would not gain the next precision), and grudge is not an SA, so precision should be even harmful against it. There's Primed of course, but AI is bad at spamming tears.
It would be interesting if it also mirrored your debuffs to the opponent. Then it would be an interesting counter to the stunlock crowd and probably Bloodbath depending on how debuff transfer logic works. Would also occasionally be funny on defense if AI managed to transmute properly.