I'm going to say something controversial - not because it is necessarily true to the question of the OP, but because it's floating around my head, anyway:
Shield and flux mechanics.
Flux is an amalgamation of heat, power, shield use, shield being hit, fighter setting, phase energy etc. It works, but it could work just as well having several counters for various things. Heat dissipation could be a problem for ballistic weapons, power grid could be a problem for energy weapons, CPU cycles could be a problem for missiles. Venting heat could be a separate thing from downclocking weapons to not stress the power grid, etc. Venting flux is very all-or-nothing, and flux management is also pretty simple.
There's a single efficiency stat for shields. All directions that shields cover, they cover 100%. All directions they do not cover, they do not cover at all. There's no advantage to hitting shields from different directions, or advantages for hitting the bubble straight on at 180° for kinetic damage vs. glancing shots. Different ships could have differently shaped shields with different strong and weak points, different capabilities for handling burst damage or various damage types, different dissipation curves, differently placed shield generators...
To answer the question more honestly, I would probably pick interaction options. Like setting up outposts and mines on asteroids and planets. Setting points for friendly faction fleets to protect or patrol. Sending fleets to attack. More options when you attack stations & planets. Social interactions etc. More tactical overlay options like in previous versions.