[Jourin]

The mod I designed for me has some primitive tech called Space Travel and Basic Propulsion.

Space Travel gets you a Space Plane with three engines 100KT. Basic Propulsion gets a Nuclear Engine that cost 5X ion and burns 2.5x fuel. Basic Propulsion 4, plus Physics 1 gets you Nuclear Fusion a little better engine. Basic Propulsion 6, plus Physics 2 gets you the standard Ion engine.

Since I am using Physics for propulsion I bumped all the other physic prerequites by 1, ie shields are now Physics 2.

Space Travel 2 gets you the colony ship and Space Travel 3 gets you the small transport plus a small armed merchant ship (ie a small transport modified) With construction 1, industry 1, and Space Travel 3 you can now research ship construction.

This slows down the rapid expansion and makes the homeworld system much more important. Of Course I had to modify all the AT Reaserch files and some of the ship construction files.