This idea came from how CC:R-Polymer works, the idea is that vanilla players will see the polymer port version of the blocks, but if the client has the CC:R mod, it could show that player the standard CC:R items and interactions,

This feature would allow for "hybrid" server/client mods to exist, where they exist serverside, the client wouldn't need the mod, but the client would be enhanced if they have the mod it is better!

This can be done already, but requires mods to implement logic themselves