I won't address the details of implementation, but rather the over-arching philosophy that (should) inform the mechanics:
Defining Morale (momentum
or momentum+will power)
Is morale simply a feeling good/feeling bad about recent events as a "momentum" sort of quality, or does it reflect a broader "I can dig deep and be a champion" sort of mental energy and will power as well?
It seems to me as though many folks assume it is the former, and this is a part of why many folks are dismayed when their dot rushes for 350 yards and 6 TDs but has abysmal morale at the end of the game. If morale is more of a mental energy measure, then this might make sense...he left it all on the field that day.
fwiw, I have always assumed it to be more of the latter, and as such the current morale system has never really seemed wrong to me (though it is unbalanced in certain cases...offense vs defense in particular).
I prefer the "mental energy" model, but the important thing is to make sure that there is a coherent guiding philosophy to morale and that the GLB populace understands it. In particular, the "mental energy" model supports a per-play decrement to morale rather then a simple swing based on individual and team events...again, I think this is more inherently balanced.
Feedback LoopsOne thought in terms of balancing morale...any sort of self-reinforcing feedback looped (aka the "morale spiral") can be inherently imbalancing and lead to more blowouts, and two flurries of sacks and interceptions. While these should occur from time to time, I do think any system ought to have a safety net of sorts....for instance a player should perhaps be immune to further morale loss for a short period after suffering 2 consecutive morale damaging plays (an OT for instance needs a bit of a "floor" to prevent him from becoming a worthless rag doll after two sacks, simply for game balance purposes). Something should probably be done to help calm down iterative losses.
Results of poor moraleShould a player simply take a hit to some set of attributes, or should there be a qualitative effect to their play? For instance, should WRs just stop trying to block after getting tossed to the ground by CBs after a few tries? This might help prevent some of the spirals (not sure how to implement this at every position).
Offense vs DefenseIt seems that defense has an across the board edge at the moment...this should be fixed, obviously.
I actually like how morale works in general right now, i am not sure the whole system needs revision....but it does need some balancing at the very least.
Good Luck