There is already a CD on tags, it's based on the duration of the move + the taunt animation. That's pretty much how they are balancing the game with tag... the long winded moves that are good for tag result in tags having a longer cooldown. If you think of how assists work then that is how tag works in a sense.
This change wouldn't really fix getting locked down by hypers or moves that linger on the screen.
This change also wouldn't fix moves that negate advance guard.
It's possible that the tag system probably needs a CDR but all you are doing is making synergy worse but not really addressing the issue of getting locked down for 10 seconds. This is probably a more difficult thing to fix than just changing any one thing.
I have a great suggestion for the block stun problem. Make Counter Switching on BLOCK cost 1 meter and set the incoming tag partner behind the point character. This system already exists but it costs 2 bars and the incoming character comes in too far and goes back into the pressure meaning this thing isn't really useful outside of advance guardable stuff. This will work like a pseudo "crossover counter" or alpha counter that exists in previous games. Of course this will work less effectively in the corner but still this would get you out of a lot of dank stuff in the game.
Barring this, you probably need to put some restriction on tagging during hypers. Maybe make it so that you can only tag during the recovery of a hyper but that would kill a lot of the synergy aspects in the game (like Frank getting multiple camera shots during Dante's hyper or Dorm charging up stocks). It might be worth doing anyway to prevent the degenerate game play. Beyond that they definitely need to make some of the non push block moves be allowed to be pushed back.
Deader than dead.
