Between each five game series there is one placeholder day, and seven games series have two.  If a series goes a full five or seven games, there is only one true "off" day before the start of the next series.  I propose making one of those placeholder days a regular day off in each case - resulting in at least two total days off between each series.  The postseason would remain the same length and more closely replicate MLB.

Don't like this one. Teams can already get away with 3 man rotations with the right staff, we don't need additional off days in the postseason.

Perhaps pitcher recovery time should be altered.

Good idea.   Let's add one off day during the playoffs and overhaul the pitcher fatigue engine.    Nice.

I'd rather have the engine simulate fatigue more realistically than having to artificially shrink time between playoff series to compensate.  (Presuming that three man rotations isn't considered realistic.)

How about we just do away with the 55(84) numbers.    How in the hell is that realistic?   

"Hey, CC, how do you feel?"
"Coach, I'd say I'm 55% today but I'll be 84% tomorrow."

Mike your tongue in cheek response has some merit.  Yes this is a numbers simulation, but other than Tony LaRussa, how many managers can look at a player and see he has 90% in the tank.

How about something like this (refine as you would like).  95 to 100% Feels Great, 85-95 Feels Strong, 75-85 I'm feelling ok coach, 65-75 I can give you an inning if needed, 55-65 I'm a little jello armed, 40-55 Sorry coach my shoulders sore, below 40 Coach I'm gassed.

This give you some guidence but not exact knowledge of where your guys are, that way it's a little more strategy when you are considering resting a reliever.