have certain lycanthropes in the game transfer a disease
every time you age an hour, or something else if that is too long.
lose 10 hp off max hp (or more) starts a quest of sorts with no clues.
you have until you die to complete the quest, maybe the illness has some -1 timer maledictions. if you pull off the quest (i.e. complete the transformation before the disease ravages you) then you get a low rating shapeshift skill, one form, (whatever lycanthrope you were bitten by) maybe something you cannot practice, base 25% can only be done when the moon is full or whatever limits are needed.

the quest having no clues when it starts is likely to keep most people from even trying it. the probability of death if you fail will also limit the number of folk attempting it.

'course you could set up a trigger highlight on changing of the moon to full, you alter description and act more bestial. etc.. but whew what a hassle. esp. if you are fighting when it comes. keep to the rp and die while pasting the new desc? or wait til fight is done to do the change?

as for the rest: saurians are an awesome idea. (way back in the d&d days ('79-'84) I always thought lizardmen and the like should have been acceptable races. but that's just me)