My rule of thumb is to keep total time down from PDs within 10% of total.
There is one school of thought that 10% PD (including the occasional PE or HNT) is optimum. If you are more accurate than that, you probably need to speed up.
Usually it is the other way 'round.
IDPA (and IPSC) is getting a lot of novice shooters.
They hear the rapid fire and see the movement and props and think "Hey this is kewl, this is what I need to shoot." Unfortunately omitting the step of learning the basics of getting hits under straightforward slowfire conditions. Not to mention how to operate the gun.
And I wonder at things like:
"I'm just gearing up for IDPA this next spring... Agreed, I like the rules in IDPA but from what I've seen there's still too much emphasis on speed vs accuracy."
Maybe you could put in a few (or a few dozen) matches before rewriting the rules for us. I think you will find the penalties adequate for the purpose.