Derrick:
Does anyone have other ideas?
If people* want to be able to force a 'tap out', I'd say Will rolls every time some one takes significant damage once below 0 HP, or in the face of any over the top pain (Limb Lock on a Crippled Limb), a submission hold when some one has been Blinded, when two or more limbs/hands/feet/sense organs are crippled, etc.
I'd also toss some penalties and bonuses like: -1 for every multiple of HT they're below 0 HP, -1 for being below 1/2 FP, +1 if their foe has taken more injury than they have, +1 if they're above 0 HP, +1 if their foe is below 1/2 FP and they aren't. High Pain Threshold's +4 is clearly significant.
* By which I mean
every one participating in the tourney.
Half HP or more in one
turn.
Eyes and ears. Each pair only counts once, so if an eye is plucked and then the second eye get's blinded I wouldn't force a Will roll. But if one eye is plucked and then their hand gets mangled, Will roll time. Okay, I guess if someone get's their tongue ripped out, I'd count that as well.