A game kinda like Titanfall but with tinier mecha, a micromecha game, or a very interesting medieval style of game, I'll explain all three:
1: Tiny-mecha Titanfall
I like the concept of soldiers vs mecha, truly I do. But those are some big mechs. The smaller a mecha is, the greater chance that you can feasibly have soldiers able to take one down without SotC style climb-the-beast-and-stab-it's-big-glowy-neck-organs. So, make them Front Mission, or Armored Core 5 sized. They're still pretty tall, but not fuck-all tall.
Actually, what I really want, is for an offshoot Battlefield game with mechs. With the same gameplay style and stuff. With the right tools, it would be just like a vehicle- and different models of mecha give different loadouts- and you could feasibly have a system of having friendly helos drop one or two any time an objective is reached, so that to get your fuck-everything mech, you need to be working for it. Or, you need to be in the right place at the right time when your enemy decides to work for it.
That way, they don't respawn all the bloody time and it dosen't become "line up for the mech". Certain models have different weak points- and they're all pretty weak to other vehicles firing at them. Some might be able to fool a guided missile or two, but getting knocked over is a death sentence (taking a heavy-hitting shell, as from most tanks, will stun you for 3-5 seconds, taking another shell from the same direction knocks you down no matter what) and a great sniper might be able to pick you off while your in the cockpit if you aren't moving.
Nonetheless, they are war machines, and they offer more than the average vehicle. Some modes allow for "personal mechs" which allow you to pick a model and specific things about it, such as perks (like in BF3) specific to it- quad legs can't be knocked over, but maybe you want explosive shielding so that mines and RPGs hitting your legs won't slow you down. Maybe you want a teammate to man a turret, or maybe you need vertical-launch flares in case someone brings a jet. Mechs that are not "personal" are randomized.
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2. Micromecha game:
Micromecha in that they're smaller than you are. It's a "game within a game" game, where you and a bunch of other people fight with mecha on simulated battlefields about the size of a large table, up to a room in size. You build a mecha from the ground up, Chromehounds style, with the caveat that your mecha needs to be within some sort of design base- humanoid, quadruped, centipede, etc.
Mecha can be equipped in any number of ways, and purchasable parts differ greatly, as there are multiple companies that make parts. Some don't work well together, and using the same company throughout a design usually gives bonuses.
This is basically a mecha game without serious military overtones. Custom Robo Arena, but with more realistic mecha design and weapons.
3. Medieval Game
What if we take crazy mecha armor design ideas and apply them to knight armor?
I was considering doing the nanowrimo challenge, and I'm currently thinking up a nation who's warriors are lightly armored- mostly- except their legs are fairly well armored and there's a shield attached to their shin. They also have armguards for blocking with, and multiple weapons for exploiting the speed they have and ability to guard themselves in a crouched position.