CBS approvals come at a premium. They take time out of the development cycle.
Also, some assets share models... and this restricts some models from being used KDF side as races like Gorn clash with most tops that have built-in collars.
After seeing how Cryptic is separating belts from uniforms, I'd like to make two suggestions for tweaking customization in ways that would allow more diverse use of assets and easier construction (and easier sharing) of new assets later:
1) Let us pick rank display independent of uniform. This means, for example, the ability to pick between 2409-style chest pips, TOS rank stripes, and neck pips on any uniform that has these features. Now, I imagine this would be case by case and some in phases but even Paramount toyed with rank stripes. That's a ton of customization with a few assets... and I can see how alternate rank displays could also flesh out other factions.
2) Separate collars from uniforms. Once you've done this, it opens up a lot of options. It should allow Exchange BOs to wear Starfleet uniforms. Put the WoK collar on the TOS shirt and you have the Cage uniform. Remove the collar and belt from the WoK uniform and enable the TNG badge and you have the Stargazer-era uniform. You can reuse the collar from the WoK uniform on variants.
One very minor thing that gets me . . . why are there no presets for the canon?
I mean, we have an amazing thread here that shows how to make canon-accurate uniforms, but it really shouldn't be that hard. When you unlock a uniform, it should already be available as a preset. That would encourage more people to wear them.
Also, why can't I wear any combadge with any uniform?