[Suicide Junkie]

Stars! Is quite good. Its main weakness is combat, however.

A very tiny combat grid, with some ship designs capable of effectively moving all the way across it in one turn. Ship stacking in combat is also way out of control. No manoeuvering or formations, just pile on and trade blows, may the biggest guns & armor win.

Stars!, with SE4's UI, ship design, combat, research and moddability would rule. Throw in SE3 style ship construction and intel, too.