First off, I didn't read through every post so if i make any stupid or repetitive posts I will say sorry in advance.
My thoughts:
Gauss Rifle: Too much like the LR
Grenades: We have em
Poison: I love the idea of tracer rounds, probably for the CG, where after someone gets hit, they lose a low amount of damage periodically, and is refreshed everytime you are hit with another CG bullet. It would have to be relatively small, like total DoT is 15% on OR, 10% on Raider, and 5% on Sentinel, as it is not meant to do the majority of damage (numbers probably should be smaller). Also, the DoT should only be refreshed when hit again, not adding another DoT, because if a OR was hit with 4 bullets in a row, if the poison stacks the OR would lose 45% of its health purely to poison. With my idea it would refresh, probably doing about 18-25% damage depending on how far apart timewise the bullets hit the OR. An alternative is to create a max amount of stacks, but I think it just makes more sense to have one DoT. Great finishing and chasing tool IMO
Turret: Legions is all about mobility. This defeats the purpose. Too easy of a target.
Flame Thrower: I approve of this if it does moderate damage in close, and leaves a low "poison" on the target afterwards. However I still prefer a special CG with poison bullets and a sword over this.
Sword: The sword should have a lunging mechanism. Every time you "shoot", you lunge in the direction you are facing, eating up one "bullet" or ammo, and accelerate by idk persay 25m/s. It could have a cooldown similar to the RL or GL, and have a small number of lunges, so it isn't spammed. If you hit, you do something around the LR damage. It would work similar to Halo's sword (won't look like it), where you lunge towards your target, and then slow back down again, but you lunge forward, not lunge onto a locked target. I feel like if it didn't slow you back down again it could be used to make cappers OP, by replacing OD with a painless lunge. Overall, I think it would add skill to close combat, kinda like a high risk high reward sorta thing.
EDIT: Another possibility is that the sword has ammo, but uses up energy continuously, as you could hold down the lunge for as long as you wanted to or ran out of energy.
Chainsaw: Useless. Requiring one to stay up next to someone for a continous period of time is ridiculous. Or if it does high damage quickly, it would be cheap if someone blew by you and you ate away their health in .1 seconds. Plus, how would ammo work? Sword ftw
Shotgun: A shotgun would just be an OP close combat weapon. Assuming that a shotgun has a very small range but does high close combat damage, I feel like it would make a sword pointless and ruin dueling. In duels I almost always get very close to a person. If we both have shotguns, its basically whoever has a faster trigger finger who wins, not any actual aiming. I just feel like this is the lazy man's weapon, and would just make dueling a shotgun timing fest.
Idea: Godsend (call it whatever you want, probably a mortar or light missile or something, I just think that name is cool

)
I feel like theres a lack of long range weapons, as their is only the LR. The RL can kinda be one, but thats more luck and it isnt really meant for it. This is where I came up with the idea of Godsend. A laser pointer comes from your gun, and can see the laseruntil it either hits the ground or goes out of sight. If the LMB is clicked, the beam pulses, and after ~1 second i wide Laser beam is comes from the sky straight down to where the laser ends, and has a cooldown similar to that of the LR. This ground pounding but for long range. I thought the beam should be wide because it would be very hard to judge where and enemy is while in mid-air. At its epicenter damage equal to the LR is done, and the damage drops off from there (amount of damage can change, I don't really know how much it should do). There are two problems i see: 1. Depending on the width, the beam could be either extremely easy to aim, or extremely difficult. Solution: That's what game testing is for

. 2. If you are aiming beyond where you can see, it would be cheap to hit someone like that. Solution: This is tricky. Either the damage could drop off at large ranges like the LR does, or it could simply be unusuable if you are aiming too far out.
Conclusion: I would like to see refreshable, nonstackable DoT poison special CG bullets, a sword for lunging, and possibly a Godsend. I love that name