One thing that IMO should be noted is that in ToEE, due to to the lack of implementation of high level feats, from lvl 16 to lvl 20, all a monk gets is 10 movement and 1 AC. So a monk 15 / xxx has a lot more chances of being stronger than anything with monk 16-20 in it. One very strong combo is: 5 rogue /15 monk gets 3d6 in sneak attack And the one I think is the ultimate Monk in ToEE: Human 4 fighter/1 barbarian/15 monk - 3 extra feats, d12 hit dice, 10 movement, rage, uncanny dodge, survival skill This one is highly flexible due to all the extra feats. You only really start to use it by lvl 10 or so thou... until then he is a regular fighter-type. And it will take some time to regain the AC you used to have until lvl 5 when you had armor on. Or you could invert it and play the 15 monk levels first. That would probably make it more fun and challenging, and by the end, you would still have a major ass kicker. "Idea for a duo-run with a Heironeous Paladin and This guy as a Hextorite...."
Except this build is by rules impossible: Monk HAS to be lawful, Barbarian HAS to be chaotic. Unless using console... ( Heck, I once made a paladin of Kord ! On the bad side tho, the game was crushing A LOT! There's a reason why console is not advisable.. )