I'm sure this point has been raised a few times, but.....Why not change the way Monk Multiclassing is handled? I get that Monk mixed with certain classes (druid being an obvious one) is bonkers, but it seems draconian to utterly deny -any- multiclassing. There's a wealth of possibilities there that just can't be done.
I can see three viable ways to do it:
1) Make 'Monk / Any other class' something that needs an application to do. Not an ideal choice, due to the extra work it would give the Council. But still an option.
2) Only allow a few classes. Monk/Fighter? Monk/Rogue? Monk/Bard? Only ones I wouldn't allow really, are Druid/Cleric/Paladin. Not a bad way of doing it.
3) More stringent required levels. You need -at least- 10 levels of Monk before you can Multiclass. Roleplay-wise : At that point in your capacities, you can say you mastered the basics of monkhood.....And can maybe branch out.
This also seems like a good way of preventing the more OP builds. Shoot, even 10 Monk/10 Druid would be pretty dope, but it wouldn't have the insane amounts of power some of the greater wildshapes would have of a Druid lvl 12. By the time you would have, say, Claws of the savage, you'd be lvl 17. Same for a wizard's Haste, cleric spells, ect...