Dark monks get higher level damage attacks, light monks do not.
Prestige classes dont count. (Too obvious to explain why)
And rename Fists of Light to "Fists of cure light wounds and undead bane" - because it is not light damage.
Or just be logical and make the damage light damage - that can still heal. There is no logical reason light monks get no other light attacks except at level 3.
Then add a level 12/18 set of light attacks - top tier doing 5d6 light damage say per hit. With a finisher that is like sunburst say.
Kame...meha!