I don't think 3PP should try to beat WotC to a power source. Primal, Psi, and Shadow are all but confirmed; Ki is strongly suspected. If a 3PP does their own version of Primal, no one will buy it after WotC comes out with theirs. So they should either try to use existing power sources, wait for WotC to create theirs and then use those, or invent their own that WotC is unlikely to come up with. For instance, a "magitek" power source might be appropriate for a steampunk-type setting (though the artificer might go there when Eberron CS comes out), or a "purity" source for an Arthurian setting, or whatever (Book of Erotic Fantasy, you've got an easy one), but I agree that the Big Book of Source/Role Combinations WotC Hasn't Done Yet is a poor idea. Above all, it's more important to first come up with a class concept, just like you'd do in 3rd edition, and then fit a role and power source to it post-hoc. You can bet that's what WotC is doing--if they'd wanted to launch with the monk or barbarian, they'd have made them martial; if they'd wanted to launch with the druid, they'd have made it divine; etc.