1. Visible angle indicators for aliens with wallwalking. Like the game Alien vs Predator has. Maybe it has been discussed before, I don't know.
Would be helpful, but if you play a lot, I think you learn the maps and ceilings a well

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2. Making energy weapons not buy energy instantly, but over a little time instead. Would make repeaters a little less useful. Could also be done to only affect repeaters.
Repeaters are underused as it is. I think it wouldn't be a good idea to cripple them more.
3. This I know has been pointed out before, but I want to reinstate it. HUD-reading for buildings. Either for builders or everyone.
Good idea, if I remember correctly, we all agreed that this could be it. OM and Reactor should be visible for every Human/Alien, as well as their health points.
4. Modifying armory interface. I feel that selling equipment is pointless, except for grenades. Could be done that it automatically sells what's needed when you buy something, instead of making you first sell and then buy something.
You're absolutely right, it's annoying and deceptive for newbies. There's no logic in the system it uses now.
5. De-evolving. I know it has been said that you don't like the idea. But I think it would be more balanced to include it, as humans already have the system. It's especially annoying for tyrants that can't get to certain locations, to lose evolve points, when it could have been unnecessary.
Not a good idea, imagine Dretches pouring out of the vents, then popping to Tyrants :-? .
6. Evolution timer. Maybe 5 seconds or so. Probably been mentioned before.
Have been rejected, I think. It's not a must-have, anyway. And could be annoying when leveling the enemy's base.
7. Flashlight upgrade for certain weapons. Could not only be used to lighten up areas, but also to mildly blind aliens. Seen it was turned down before, but it can never hurt to ask I guess.
Not necessary, it would only make you use another button

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Gamma on standard settings:
Gamma I am using (2.0) :
8. Making Mass Driver more useful. Been said a lot before.
Yes, Mass Drivers aren't as useful as they should. It kills a Dretch in one shot, but it has a high load time and small clip capacity. I think devs wanted to make them sniper-like slow-firing but powerful weapons. But in Trem, there aren't places for snipers (luckily).
9. Radio commands. Has also been mentioned before, but I support it as well.
We all support it, I think.