Like I said earlier in other keycap threads; it is best for the organizers to provide start off with the base alphanumerics instead of a TKL.
The number of 60% users and sub-60% users here are increasing, and I believe that these crowds are insane drivers for SA profile keycaps.
Personally, I'd prefer if we can keep to Row-3 uniform (easier to switch layouts between QWERTY and Dvorak/Workman/Etc.) and for the benefit of the Ergo crowds also.
In the end, the main reason for my preference is because I don't like to see wasted caps, and people can just buy the caps that they need to complete the board that they want, instead of having a bunch of keys that are sitting in a drawer somewhere.
So, my idea would be:
1. Base kit: Alphanumerics and punctuation only.
2. 60% kit (modifiers mainly)
3. TKL kit (function row and navigation 9-keys)
4. Numpad.
5. Novelties.
6. Ergodoxen kit (blanks are best, since there are as many layouts as users).
7. Tsangan mod Kit.
8. So on and so forth.
You get the gist of it from the above.
However, this is not without drawbacks, as Matt3o once commented that such a distribution of caps might eventually be more expensive than just buying the TKL set and tacking on the addons instead (and having leftover keys).
Of course, you need to understand my current background is that I am mainly using a Lightsaber (until it is collected) and an Ergodox. I have a baggie for each GB that I participated in that contains the leftover keys that I will never need.