I suggest some trainable attributes that have a random starting point, like stats. They could make difference where the the fight will stay (stand up, grapl, clinch).
Since we have offence stats in Right/Left, some general defensive attributes could be good, maybe there could have different daily spars than current spars for right/left.
Blocking/Dodging - Together or separated.
Takedown Defence -
Clinch Defence - Transitions, also break clinch.
Grapling Defence - Transitions, also would help them stand up.

I saw some perks in the UFC 3, most are covered in atual game (styles/stats), but some could add something to the game. I dont mean to copy anything. We could change the names and/or function or add some new ones. They might start with fighter (for ex 1 or 2) and be developed throught training (our choice), having like a max limit per fighter.

Perks (Ideas)
Grappling
Dirty Boxer - Punches and elbows deals more damage in clinch.
Escape artist - Improve ability to escape submissions.
Ground and Pound - Increase damage of strikes on the ground.
Guard Specialist - Improve transitiong speeds in any guard position.
Judoka - Improves hip and judo throws from the clinch.
Nightmare - Improves finishing submissions when on the top.
Off the Back - Improves finishing submisisons when on the bottom.
Slam Boost - Increase damage for all power takedowns or throws.
Thai Terror - Increases damage from knees in the clinch.
To your Feet - Improve ability to get to their feet.
Work Horse - Improve top position control in side control, full mount and stack guard.
Wrestle Clinic - Improve attempts for all single leg and double leg takedowns.

Stand Up
Counter strike - Improve CS
Crazy Legs - Speed up kick counters when kicks are blocked.
Fluidity - Improve combination speed
Head Hunter - Damage on head kicks
Heavy hands - Damage on hand
Laser focus - improves accuracy of punches when opponent is whobbled.
Risk Reward - Faster strikes when oppponent suffer a health event
Rush en - Increase damage of running punches
Steel Checks - Boosts damage from succesfuly executed leg blocks.
Tree Chopper - Increase damage when throw leg kicks
Untouchable - Improve fighters ability do slip punches in first round
Vengeful - When suffering a helth event your strikes deal more damage
Zero In - Increase accuracy when performing consecutive strikes

Fitness
Crushing presence - Reduce opponents stamina when in top position.
Desperate measures - Stamina loss is reduced during health events.
Force of Nature - Delay opponent's recovery after a succesful takedown.
Grinder - Gain stamina boost while in clinch
Higher altitude - Increase Stamia in rounds 3 to 5
Marathoner - Stand up is more efficient when moving
Negative reinforcement - Defending takedowns reduce opponents recovery.
Opportunist - Stamina boost when opponent is in health event.
Tap already - Improve effiency of attempting submisssions.

Health
Atack the base - Increase chance of causing limping with leg kicks
Body Snatcher - Increase ability to stagger opponent with body hooks.
Carved of wood - endure more damage to legs when limping.
El Guapo - Inrease the ability to stagger opponent with core body kicks.
Game changer - Increases abilty to wobble opponent with overhand punches.
Taekwondo - Increase ability to stagger oppponent with spinning head kicks.
The Butcher - Increases ability to stagger opponent with front and side body kicks.
Wake up call- Recovery is boostend when staggered to the head or body.
Weathering Storms - Fighters can endure more damage to the head and body when hurt.