Stop worrying about loot.

This might seem a bit callous, but practically speaking -- both as a raid leader and as someone who regularly PUGs raids -- I would highly recommend simply taking the hit and accepting that DKP is not going to happen for loot distribution in those raids. Unless you have a regular set of PUGs that you keep inviting back, you should just switch to a /roll based system.

Assuming the players you're pugging are approximately equal to your guild players, you're likely only giving up 20% of the pieces that might drop anyway -- and those players are making it so that you can keep gaining loot, and everything else you need.

Establish decent loot rules at the start -- for example, "Mainspec rolls first, offspec rolls second, mainspec priority to those who haven't won anything, tier tokens and saronite stay in guild." Generally speaking, these types of rolls will be acceptable to most PUGs, and while you're PUGging, your guild can keep learning, and gain badges, as well as still picking up most of the loot from the runs. Even if a couple pieces get grabbed by a PUG, you should still have a decent amount of loot progression in guild, and it's much better in any case than taking the night off; badges, practice, and experience working together will help you out in the end.

(If the PUGs you're inviting are significantly differently geared than you, you may be bringing the wrong PUGs.)