I'm not necessarily pro-mech, but I'll play the Devil's advocate for the sake of the discussion.

I imagine the mech to be a larger and more menacing vehicle which would do more things than an HAV. Not only would it have offensive capabilities, but it would be very mobile. It would be a moving spawn point and would have massive health. It would have the capability to have both anti air, anti personnel and anti ground vehicle. The real downside would be the massive cost and how large of a target it would be.

If you brought out a mech and thought it would win you the game then the enemy team could bring out HAV's, turrets and anti MANPADS suddenly your giant mech is disintegrating on the ground and the battle just hot a lot costlier.

I'll disagree with that point since a lot of weapons in Dust 514 were extremely redundant. For example, the regular rail rifle was superseded by the assault rail rifle in competitive play, then you had weapons like the burst Scrambler Pistol, sleek locus grenade and the Plasma Cannon. All were theoretically viable, but in practice they were all either redundant or so since specific nobody ever needed them ever. Myofibril stimulants were also pretty uneccessary until they were given the ability to increase jump height. Nova Knives were also redundant since technically their job was already fulfilled by the Breach Shotgun and the only thing that kept them relevant in the slightest was that there was never am advanced or prototype version of the Breach Shotgun.

I think the entire "practical" approach to equipment design is BS.

Anyways, the ISK thing would only be a secondary deterrent. The first and foremost deterrent would be that if the enemy team could knock out the mech with their counyerasures that continuously calling in mechs would be useless. At that point it would make much more sense to simply use smaller concentrations of forces to engage the enemy in multiple smaller engagements on the battlefield where it is more difficult for them to coordinate.

It's basically the reason we don't use zeppelins in war anymore. Having everyone shooting at one target kind of negates the purpose of it entirely. Only if the other team can successfully counter their countermeasures could the mech actually see a good use.

But mechs have a 1-man crew. IMO, the more crew members a vehicle can have, the more effective it should be with all of them.

Honestly, mechs are a bad idea in general because vehicles are a force multiplier- any vehicle that can be effective with a single crew member is inherently OP because there's no downside to using them.
If you have 7 people in a dropship, that's 7 people that could be fighting elsewhere. However, the dropship can potentially make those 7 people far more effective if they're coordinated.
That wasn't the case with HAVs- an HAV could be effective with 1 person, and it made that 1 person far more effective with no need for coordination of any kind. That's why HAVs were so much better than any other vehicle.

So, my main point: single-person vehicles (or vehicles which a single person can be effective in) must not be added unless they have a glaring weakness to counteract how much more effective they make a player.
My idea: make an incredibly weak "pilot suit" which is required to operate single-person vehicles, and make some vehicles much more vulnerable to AV than vehicles that need actual crews. I'm saying make the pilot suit extremely weak so we don't have the pilot jumping out and gunning down AVers like they did sometimes in Dust.

Your going about it the wrong way. You think of a feature for the game first, then think about how it fits into the universe. Otherwise, one could argue about plenty of things in ANY game including eve on "Why would they have X if they have Y?"

Anywho, mecha would be fun to use. They might be sort of a scout vehicle (good mobility, decent attack power, low eHP in comparison to other vehicles). A HAV would be a Sentinel.

Also, I found it kind of dumb to have vehicle repair tools because you can call one in and send the other back, and you can't keep up with a vehicle to actively repair under attack. Give MTACs a support role to both infantry and vehicles. To support infantry, they could be fitted with a HMG with very low heat, but has terrible accuracy. In other words, keep the pressure up on enemies, but not become an unstoppable death machine upon deployment. Alternatively, they could be logistics and have vehicle repair tools similar to the focused where they could only focus on 1 or 2 targets, but repair at a decent rate, while logi vehicles would be the one that has plenty of beams, but poor repair rate.

Sorry for the wall of text.

Haha sorry! I rarely read past the first page.