Some opinions on mechanics
Movement
So humans have some movement capabilities, but at the moment they're pretty much in the mode of 'you can sprint around the entire map and still have 50% hp, but if you try to strafe-jump, you lose craploads of stamina for a bit of extra speed.' I think a great game to look at in terms of movement is Urban Terror. It feels very good in that game, especially the sliding (which we unfortunately can't copy without it looking completely obvious that we just cribbed it from them). If you don't know how UrT movement looks, have a look at some random gameplay footage. It's a lot of strafejumping, but it's capped by stamina which regenerates fairly fast while crouched/walking/standing. The main way people move is 'strafe jump some, then walk until I have stamina,' which is nice, because people can move quickly around the map, but they also have to manage their stamina so they don't get caught with no stamina and no movement. You also make a loud breathing sound when you have low stamina, which is nice for finding people who just sprint around the map until they're out of stamina :). I'd really like to do something like this for Uv, because it introduces an amount of strategy into the game, and it also increases the stealth mechanics, which I really like. (Imo, the radar updates have been the best gameplay changes so far, because they increase the stealth mechanic for humans, which the aliens previously had a monopoly on). The main things to fix in order to encourage this playstyle are to decrease the available stamina humans have, or increase the stamina drain sprinting takes, and increase the walking recharge rate.
Stealth
I like the direction this is going. It's very cool to be finally able to ambush aliens. My favorite part of trem was always hiding as a dretch, and then killing some witless s1 humans from behind. I think a good extension of this would be to make the basi a better stealth fighter. At the moment, it's a weird cross between a stealth class and a healing class, simultaneously pressured to lie in wait behind human lines, and heal people from behind alien lines. You can guess what most people choose to do... A cloaking mechanic would really enhance the class, and might be a great adv ability. Getting rid of healing would allow it to be better at what it does, while not taking away much from the class experience (you don't even get points for healing...). The mechanic of the basi should also be changed. The (base/with no upgrades) spy in tf2 is a good example of a stealth class done right. He has a high skill ceiling, can kill people who aren't completely on their own, has a few methods of escape/infiltration, is no good in up front fighting, and doesn't feel completely OP when the game works correctly (the melee hit detection in tf2 is notoriously bad, especially with spies). The basi suffers from being very weak in crowds, and tends to feel cheap when you have him just outside of your range of fire but you can't turn to kill him. This is not good, as leaving people unable to effect their own deaths while they die is a Bad Thing (TM) (Imo, the trapper has this too...). In general, locking people's fov is annoying, as people like to be able to defend themselves, if not shoot at things. Anyway, another kill mechanic is needed. I'm not sure what would work here, but it does need changing.
Weapons
I have posted previously about where I want to go with weapons, but I'm going to elaborate. There will be a slot system similar to many fpss. There will be the main weapon slot. There will be several weapons to chose from for each class, and they will all be different except for the ckit (although most buildings could be limited to being built by the marine). There will be a sidearm slot. This will have various pistols, as well as medkits and maybe a mini-ckit. All classes will have the same sidearm slot choices. The melee slot will be constant and different for each class. There will also be an upgrade slot. I'm thinking of this as a misc slot. It could contain grenades, bombs, or invisiwatches. Or jetpacks and battpacks. The point of this slot is to allow a greater degree of customization for people.
Classes
Each class should be good at something. The Agent will be good at stealth and sniping. The mecha will be good at taking and dealing damage. The marine will be good at building bases and supporting his teammates. At s1, the marine needs to be able to attack the alien base, and maintain the human base. He needs to have good damage against s1 aliens. At s2, the agent comes in. He has already been outlined as a stealth/sniping class. This means that he should be able to work well with the marine in order to take down larger aliens. He should not be all that great at taking down advanced aliens on his own, but rely on the marine to provide distraction and support. He should be able to deal with s1 aliens more easily than the marine, though. As he is a stealth class, he should also be good at recon if the player so chooses. The mecha should take over from the marine as the main damage class at s3. The marine shifts more into a role of support and base maintenance while the Agent remains in the same niche as before. The agent and the mecha should be very effective at basekilling at this point. (Side note: maybe cold blooded killer isn't the best archetype now that I think about it :P).
Buildings
Defensive Buildings should be tougher as individuals, but there need to be less of them. At the moment, a mara can hop through a h base and zap stuff while leaving with 50% hp. This is due to the obscene amount of spinup turrets have, and it makes bases not very scary. As an alien, a turret or two is no sweat to take out. Now this is ok at s1. Aliens have to be able to dance around the turrets and get within melee range to do damage. It works out because there is a high risk/high reward for aliens. At s2, there is the goon. The goon can take out 1 ret with 2 barbs, possibly while taking little to no damage. Now there is a small risk/high reward for aliens. There is now a very long time (up to 20-30 seconds, with bp regen and build time) to regain what a single goon took away in 5 seconds. With 2 goons and a source of healing, all bases fall unless humans kill the alien base. If humans want to prevent the goons from killing rets, they have to camp, and that allows the aliens to build them in with fwd bases. If they don't camp, their base gets killed. It also feels very futile for builders to keep rebuilding the exact same ret over and over again. I suggest that a new turret be available at s2. It should cost more (14-18) bp, but be more resilient (a goon has to unload his barbs and take a chomp to kill it, thus making basekilling once again high-risk/high-reward) and not suffer from spinup. The downside would be reduced dps. This gives the humans options as well when building bases. Teslas are only really good at doorways, so bases tend to be 5-6 rets and maybe a tesla. Having a new turret would give builders options as well in terms of base design. What's the best number of rets? Where are new rets better? The metagame could use some changing and this would really be nice. On another note, a building to change classes at a cost (credits or time or both) would be interesting either as a separate building or as an upgrade to the arm.
</wall>