Any suggestions on invested characters I make would be self-serving - and probably not be better for the game.
I play Kotal, Jax, Jason, and Ermac. I could think of lots of ways to buff these guys, but I have a dog in the fight - so I won't suggest anything.
I hate playing Kitana and Kung Jin - and would love for these characters to receive nerfs, but any suggestions would be jaded - so I won't speak on them.
The suggestions I do have are to buff the characters that are unviable to the point where they a lot more bad matchups than good ones. Examples of these characters include...
Goro (overhaul)
Takeda (get rid of the gaps in his strings and give him a safe wake-up)
Fisticuffs JC (just rollback the nerfs)
Examples of characters needing lesser buffs include...
Reptile (slight, just a little less damage scaling on his combos)
Sub Zero (just tweak the clone a little)
Mileena (just give her a safe string or make her roll hit low)
Kano (just enlarge his hitboxes a little and improve the Choke on block in Commando)
Predator (slightly increase the damage scaling on his longer combos)
Jaqui (enlarge her hitboxes on her openers a little)
BTW - Here are the self-serving suggestions...
Kotal Khan (make his deflect reflect projectiles)
Mystic Ermac (scale back the damage scaling on his Tele-Hang)
Jax (just don't nerf him)