First off, I don't have the knowledge, the time and the resources to organize a group buy, I never have and never will, so I'm not teaching anything to anyone here, just sharing my opinion if it's welcome.
What I would do, is to split the GB into two separate ones. One for mods and one for alphas, although this might lead to problems with the numpad.
As for the mods, billnye's
Electric Bluegaloo is simply the best example and advice you might seek. I would just replace the very first key with an Esc and add a 1u Backspace.
Also, I would leave the gamer kit out for a two main reasons: They have to match the mod kit so they are likely to end up in it and people would find themselves paying for it even if they don't want it. Secondly, a gamer kit is strictly QWERTY which wouldn't match international kits, if you plan any, such as AZERTY, let alone Dvorak or Colemak.
Lastly, if you're going for Alphas alone, check interest on international kits.