I think the set lack contrast making it too dark as a whole.
The purple is a novel idea,
I would recommend testing yellow alpha with purple font or at least adding in a yellow space bar or more yellow mods be it in the F row or something like that
To me, the main attraction of this set lies with its monotone keycaps, with the exception of the Enter, Esc, and Arrow keys. Changing it to have a colored mods or fn rows will just make this set like any other sets out there with different colors.
As for the colored spacebar, I think it was mentioned before that adding it will increase costs, with the unspoken agreement that colored spacebars will be offered in a separate child kit instead.
Plus, I think the price for the base kit would not be cheap, seeing how huge the current base kit is. Creating a separate child kit to accomodate more colors will make more sense. Even so, there is always a challenge of meeting MOQ for each kit (100 for child kit iirc).