Here are my suggestions for your proposed keycap sets:
If you plan to move forward with an Interest Check, one big missing factor here is the keycap profile. You need to decide on SA, DSA, XDA, Cherry, DCS, or Cubic. Those are currently the options for custom keycap sets.
Once you decide on a profile you can start to look at a manufacturer. Unless you plan to sell a LOT of keycaps, you will probably need to pick colors that the manufacturer has available (instead of a custom color). Your colors are primaries so I don't think you'll have issues using stock colors with any vendor.
Because you've chosen to have white legends on darker colored keycaps, you'll need to look for a manufacturer that can produce double-shot keycaps. This is done with ABS plastic.
Profiles and their Manufacturers---
SA: Signature Plastics or Maxkey
DSA: Signature Plastics
DCS: Signature Plastics
Cherry: GMK
Cubic: Tai-Hao
I probably shouldn't list Tai-Hao or Cubic b/c only recently has anyone tried to get this done, but I would say your project could get interest by being unique if you go that route.
There are other manufactures out there. I know there are some Chinese compaines making DSA profile caps, but I've only ever seen dye sublimated PBT caps. The ones listed above are your best bet.
Many keycap sets that gain popularity revolve around a theme. Your theme seems to be primary colors, but I don't think everyone could afford to get all 3 colors. It would be tricky to hit a minimum order quantity from any manuf. with people picking and choosing from 3 different colors. I would try to run an Interest Check and see which color people prefer the most and stick with just that one. (I like the yellow one the best)
A lot of people like for a keycap set to have novelties that make it unique. Something that relates to your theme, so think about that as well. Add something unique to the modifier key legends perhaps.
Also, if this really picks up attention and you plan to work hard to have a set produced, you will want to get a professional rendering of the keycap set done to make it look nice and worth people's money. The ideas you have here are fine as a start, but you need something more realistic if you get serious about it.
Hope this helps.
