I'd suggest that you should automatically get blueprint (or "mock up" or "dummy") versions of every race specific tech you design. Ships can be designed with mocked up parts, but they can't be built until all of the dummy parts are replaced by fully developed ones. Until that happens the whole ship design is flagged as a mock up, making it ineligible for construction. When the RST is fully researched, the real version of the part would automatically replace the mocked up version in any ship designs you've made. That replacement may make the ship design eligible for construction (if it doesn't have any other dummy parts).
Probably this can all be done with a simple boolean flag added to ship components in the database. When the RST research project is created, it would create the component in the database immediately, with the "dummy" (or "blueprint" or whatever) flag set. When the tech was fully researched, the flag would be unset, making the part valid for normal use.
Ship designs that include dummy parts in their design could also have a dummy flag in the database, which would be recalculated each time one of its dummy parts gets developed (or when you edit the design by adding or removing dummy components). I suppose the ship design could just check the flags on all of its component parts any time it needs to know if it is eligible for construction, but I'd guess that caching the value would be more efficient.
There would probably need to be some minor UI tweaks for how dummy parts appear in ship designs (and perhaps also how mocked up ships designs appear distinct from fully developed ones). I'd suggest just prefixing the name with something like "{MOCK UP}", but exactly what text is used doesn't really matter that much.
The only special case I can think of would be deleting RST research projects. I'd suggest that the player not be able to delete a project if the associated dummy components are being used in any ship designs. Alternatively, the game could remove the components automatically from all designs that include them, but I'd expect this to be more disruptive. Or, I suppose you could allow "orphaned" dummy parts to live on in some way, but that just seems like a bad idea to me.
Another question might be whether or not the mockup system should be extended to non-RST components. For instance, it might be nice to be able to mock up a fighter before you've researched all of the miniaturized fuel tank and engineering bay components, for instance.