I'm going to agree with you. so far I've seen CoH focus mainly on adding new combat gameplay. New zones to fight in, new enemies to fight, new powers and ATs to fight with, etc. Cryptic never seemed like a company that would put a feature into the game that didn't in some way affect how combat is played. Inventions or skills or whatever you want to call them must eventually have some kind of purpose in combat. I don't want to list any of the millions of possibilties for inventions, since the Red Names have posted precious few bits of info about the out of combat aspect of the system. But I would make the safe assumption that the system would have something to do with either bases or costumes. So far the only thing that the devs spend time on outside of pure combat or combat zones is costumes. They keep us content with tons of new baubles and doodads to throw on our tights. Bases are something that affects combat directly, simply because you can fight inside them. I would hazard a guess that inventions would affect the performance of the base and its defenses, or give attacking heroes some ability to bypass defenses.
But again, all my guesses are pure speculation and just me dumping out some thoughts, no point carrying around ideas in your knoggin' when there's an infinity of text to put them in
