[spoon]

A cool thing from the fantasy mod was to give each ship hull its own research branch. For example, in this mod, after you discover "Frigates" through regular Ship Construction research, you could open up a branch of research called "Frigate Improvements". Improvements could be along the lines of cheaper hulls, slighter bigger hulls, more engines allowed, higher defense/offense, hull specific mounts, etc etc...

Should fit well with your tech gridding you're already planning...