Precise per-machine clocks for Factorio 2.1 and Space Age. Native local effects for production/research, plus clocked pump and electric inserter variants.
Providing the player with new tools or adjusting the game interface, without fundamentally changing gameplay.
Separate planetary starts for multiplayer in Factorio 2.1 and Space Age. Give every team its own full planet set, keep teams independent, and fix Factorissimo borehole pumps on copied vanilla planets. Unofficial GPLv3 fork of Team Starts by RedRafe. New saves only.
Mods introducing new content into the game.