1. Tech upgrades require tech.
You need a tech HQ to build tech 2 tanks and tech 2 factories, right? Well, a tech 2 factory and/or tech 2 engie upgrade should be required to upgrade mex from tech 1 to tech 2, tech 2 to tech 3, etc. Same for radar, shields, etc. Why can you upgrade these things before you have the tech? It makes no sense. Also solves the balance problem of eco a little bit.
2. T3 mex cost less, ~1600 mass, and produce less, ~12 mass
Half the reason this game is so turtle is because it cost SO MUCH to max out your economy. Lower the cost of T3 mex so that you can max out your economy faster, and make them produce less to balance. This game isn't sim city with robots. Let's make fighting go faster.
3. SCUs cost more (~4 or 5k) and come with teleport ability as standard.
Anyone who's Telemazer'd someone knows how much fun teleport is. Teleport was SUPPOSED to be a central gameplay mechanic is supcom. Hell, the ENTIRE CANON is based around quantum gates and teleportation. It would also liven up the end game quite a bit. I personally think it would be awesome if quantum gates could teleport groups of units too (like in that one mod) but one thing at a time.