In that case, I agree, and retract the idea to allow them to switch guilds at all. If Polymath is easy to level in, and we allow switching of guilds with retention of level you run into the same problem as with dev reimbursement for knowledgeable players. If I level up using only the spells in the arch-mage guild, training fighter combat skills for my combat, then switch to the AM guild I wind up avoiding the poorer devs of the AM guild and the difficulties of early combat in it (although I'm told that guilds no longer modify the hp/mp players get... which irks me for some reason), without losing anything of note. This would be compounded by reimbursing devs for lost skills, but not circumvented by not reimbursing the devs for lost skills - all it would take is knowledge of what the guild you're transferring into has before hand.
The other option is to actually give Polymaths a skill/spell/ability that reincarnates them into another guild (either of their choosing or that is closest to their current training) and imposes some penalty on xp or devs. I think a skill trainable with every dev type and a hard cap of 100% would be best - at 100% you get the least amount of loss when you reinc, anything less and you get greater losses. This would both hinder their Polymath experience (so they aren't using all their devs in xp-giving skills) and afford a way to regulate (to some degree) the power level upon transfering guilds.
