Heh I feel at least moderately out of step here in some ways. I'd never heard the Gish term in reference to fighter/mages. I think all my friends still love to reference the highly overpowered Bladesinger "Oh yeah he made a Bladesinger type. Yay". Monks in 3E were ok, but I was never too big a fan of them. I remember the Psionics Handbook came out not long after Crouching Tiger and you had all these psionic combat feats that seemed like they would blend perfectly with a monk for some crazy fun. Except, to stack enough to recreate something that felt like that, you really had to combine the psi classes together. I think somewhere around here ...ah yes here it is:
Psi-Monks
as Psi-Warrior except as listed below
Bonus feats at 1, 2, 6, 11, 16, 20 *total 6 instead of 8*
HD: d8
Monk Unarmed AB based on 4's so has attacks at 5/1, 9/5/1, 13/9/5/1...follows monk's progression...4 total attacks instead of 5
Damage: 1-4: d6, 5-10: d8, 11-15: d10, 16-20: d12 *no d20 damage*
Unarmored speed: 1-5: 30 ft, 6-10: 40 ft, 11-15: 50 ft, 16-20: 60 ft
My Psionics Handbok is probably packed up at this point tho, I think I wrote that up like 5 years ago heh. Seemed a reasonable blending that would allow for more of the wuxia-inspired psi feats
I have no problem with multiclassing, but basically it has to be less powerful than 2E multiclassing and easier to merge than 3E. In 2E, you would basically be 1 level behind in both classes, but be fully capable in both and that was strong enough that most of my friends were always multi heh. Not to mention the mounds and mounds of kits. I still love the Battlerager tho. Did a decent 3E prestige ever get made of that?