there should be no pause, a parry is simply a way of not getting hit by a strike - it in no way implicitly allows a fighter more time to get off a shot.
Slipping a punch gives a better counter opportunity to counter not because you pause your opponent, but because your body can already be turned in such a way to allow YOU to strike quicker since you've already started a motion. The perfect example is slipping a right straight and countering with a left hook.
I can't remember seeing a true parry in an MMA event that led to devastating consequences - there may have been, but it's not something that should be in any way elevated over a regular strike landing. Slipping and/or rolling with punches to deliver a counter has greater effect and more than all of that 'beating someone to the punch' and landing fractions of a second before their strike is completed over powers everything.
UFC 2009 pre-patch handled all of that beautifully imo.
you don't need to give a 'penalty' to the strike thrower for being blocked/dodged/parried etc... it just doesn't work that way. Just allow counter strikes to naturally occur.
So if the effect is anything more than miniscule, it's multiplied many times over because this IS a videogame and people can't help but exploit these things because winning trumps everything. That's why I shake my head because it's easier for them to not have a 'system' and they don't seem to realize how damaging the consequences are for long-term pliability. if playing as a counter puncher is the best strategy to win in the game, that's what 90% of people are going to do especially when they find out mounting a smart pressure offensive attack that would find success in real life; is rendered useless in the game.
I hope they minimize it hard core and that I'm crazy wrong about how damaging it will be.