[Suicide Junkie]

I have to disagree with Urendi:
The main difficulty is that many of the mods are mutually incompatible.
Technologies often come into direct conflict, and both cannot be included.
Something like the sci-fi crossover would be the best you can do; all the mods jammed into one set of files, but forcing players to choose one mod per race.
If you try to include, for example, both QNP and regular propulsion in one race, your mod will not make sense, and the QNP will be ignored in favor of the more powerful regular propulsion.

Everybody has thier own vision of what the future should be like, and mods thier game appropriately.
With that in mind, the best thing to do is to make your own mod. If not that, then cut-paste-and-tweak will do reasonably well.

The Ultimate Mod (adjective, not noun), is intensely personal, with a hundred thousand facets, one for each mood of every player.