Even though I love the idea of colourful sets (I'm typing this on a pink HHKB at the moment, friends), I think we should start off with something that's more classic, so people know what they'll get, sort of. My opinion is that the best thing to do would be to make a replica run of a set with modern looks that's not very easily attainable, and therefore I think Dolch would be the best choice to start with. It may just be my imagination, but this seems to be one of the sets that are most sought after which is another good reason. :>
Then I guess you could also add in some other hard to get things, such as a red esc and rgb mods, while you're at it, but I don't think we should start off with a round 5, if you see what I mean. GMK seems like a busy company too, so a lesser order would probably be a way to get off on the right foot maybe...
I really like the idea of quarterly buys I saw mentioned earlier in the thread, since you again won't have to create the biggest group buy ever and buy sets of all possible colours at once.
By the way, if it'll be possible to get ISO sets in Swedish or Nordic layout, I'll definitely help announcing the group buy to interested Swedes! I know there are a lot of people that don't hang around GH or DT that would be interested, if only one could manage to convince them the keys will look good on their Qpad boards (for some reason 90% of all Swedish people interested in mechanical keyboards own a Qpad - crazy, isn't it?) lol.