I think this is one of those things where we can defer the decision. Let's get the first keycap set done first, then look at the resulting keycaps, look at how popular the group buy will be, and figure out what other keycap sets we all would like to do, and then we can decide.
The time frame could be like this: a month or so to collect all the adoption fees from all parents, and then another month or two to get the legends done, and done right. Meanwhile we can get the group buy running at the same time for a few weeks, another couple weeks for payment collection, and then another 1.5 months for SP to make them. And then another month or so for SP shipping, sorting, and more shipping. it could be fall or later before we are done with the first group buy based on these new legends.
We've got time :-)