i've considered this myself, partly because of the way that in the recent arcs, everyone has been so selfless about protecting komui. granted, he's the supervisor, so that alone could explain it, but. it's really hard to gauge it, because it could end up as allen, it could still end up as lenalee, even though that's been hinted at so much it seems like it must be a red herring, it could be miranda...

the biggest clue we have is that the heart is awakening. we know that the 14th is coming to life inside of allen, so that could point to allen being the double whammy, but if the heart is really someone else, it would have to be someone who wouldn't tell anyone what was going on. that could point to lavi... it could still be miranda, and she just doesn't know what's going on. it could well be komui, who would definitely not tell anyone.

however... i don't know it the Order knows. if they did, seems like... they'd react differently, i don't know. it's possible, but i think it's more likely that if komui is the heart, he's keeping that information to himself. after all, he doesn't trust the order, and the only way to know that any piece of innocence is the heart is that all the innocence would be destroyed if it was. so until the heart awoken, there was no way to be sure which was the heart.

as to whether he was experimented on... that's possible. it seems more like he was running the experiments, rather than being experimented on, but. one never knows for sure until it's canon. ^_~

frankly, i think komui being the heart would be an amazing turn of events, but. =S who knows!