But SJ...
*sigh*
Do you mean a single area of research that gives you engines and reactors? I don't know...but that's kind of a "supertech" area. Plus it doesn't make much sense to have the reactor do movement...it doesn't...it just provides "power" to the engines that do the moving.
It makes more sense to have them independent of each other as a research area but also have it so they are tied together in pratical use and should be researched concurrently...ie...better engines need better reactors...it makes perfect sense...and is more flexible than the other proposed system. I think it's the best thing since there is no true warp ability.