If multiclassed builds are allowed, I suggest equipping them with cheap items like rings of feather falling which emulate the monk's higher-level class features. Give them everything a monk has, and more. 2 levels of paladin can make up the difference in saving throws.
EDIT: Ninja'd.
Monk without monk
Rogue 4/Fighter 2/Assassin 10/Blackguard 2/Dragon disciple 2
Feats: Cleave, Improved Sunder, Improved Unarmed Strike, Multiattack, Power Attack, Stunning Fist
Items: +1 adamantine gauntlet of speed, Monk's belt, Periapt of health, Ring of evasion, Ring of feather falling (optional)
Rogue and assassin have UMD as class skills. Use dragon disciple to get two extra 4th-level assassin spell slots, and put dimension door in one of them. Death Attack emulates Quivering Palm. Your DD natural weapons, gauntlet and +16 BAB emulate flurry. The blackguard's Dark Blessing improves your saving throws, and CLW 1/day makes up for Wholeness of Body. Still rather MAD, unfortunately (needs 14 Int for assassin spells, plus Wis 11 and good Cha for blackguard).