I'm quite happy with the entire concept.
It's something innovative (for me at least).
However, certain variations seem utterly under powered (or others overpowered) compared to the other 1 or 2 a character has (Don't get me wrong, not saying something is OP in general)
In the end, this is the first time for NRS using this variation system, so I'll give them some slack cause of the issues certain variations have.
It is something they can learn from in their next installment at least, which they did from Injustice (the damage from interactables has been scales down a lot for example).
All in all, I'm happy with the concept, it's great, it's fresh and I hope it's here to stay for their future installments and I would like to see it implemented in Injustice 2 (if it will ever be) too.
Again; great concept, but the execution is a bit meh in some cases.
If I had to choose between like what, 4-6 more characters or every character having 3 variations, I'll go with variations all the way.