I'm against SP/EXP loss.. it's just frustrating to see your hard earned exp turning to smoke.. and really, it's not like if in real life you get kocked out you forget things.. unless you got hit to the head at the point of causing an amnesia lol..
I don't think gear durability loss is good either.. it'd be like what.. monsters chew on your armor while you're unconscious..? Or rather decaying..? Oh please.. xd
Weakness is generally a good penalty.. you are indeed feeling dizzy when waking up after being knocked unconscious.. during the time of weakness there could be also penalties on stats like accuracy, attack, defense and magic attack.. and also a gained SP/exp penalty.. in other words, if you manage to win or your party wins while you're weakened you get less experience due to the fact of being unable to concentrate on the battle..
Just like Hikozaemon suggested.. resurrecting magic could "relieve the stress" shortening the weakness times and reducing temporary penalties..
