Thanks, happy to hear you are liking the game. There is room on the UI probably but we are currently restricted to 8 slots, it shouldn't limit you too much though. Aren't you running out of available space once you fill your specials and weapons?
To chime in, yes we do run out of space early on. However, by the mid game, advances are increasing the space or decreasing component size, whichever, and allowing for more add-on's in weapons and systems.