As I was perusing the REG again tonight (I do that occasionally, just because it keeps me from having to do anything on the list my wife gave me), I had an idea for a deck concept, one that I'm not sure would be viable. SO maybe this is a challenge...
Build a deck using the first issue of characters that later became parts of themes and had their brigade changed. It's funny as I look over the older cards in my collection how many cards exist in two brigades. Could you even build a viable deck out of these? I don't know. Non-purple royalty, non-orange demons (my son used a demon defense before there was orange, so that can be done), non-purple disciples, non-green prophets...the possibilities are extensive.
This deck building rule would not affect the use of doms, sites, arts, etc. (unless, of course, you wanted it to).
This actually began for me with a fun deck concept, building a deck that only uses Retro (A/B/Blue/Prophets) cards, but using any printing of those cards. (That one may still see the light of day.) I might cheat on that one, and allow a couple extra dominants and allow WoNL. (Justin is ready to have me expelled from the Retro fraternity for this.)