That's why I play for the campaign and haven't touched multiplayer since 3 (even then I mainly played Horde).

A couple weeks ago I was bored and tried writing out the rules for a grand multiplayer mode as you describe. No clue how the hell it would work in practice but it sounds fucking sick on paper. An asymmetric, class-based, combined-arms all-out war game--BF style Conquest/Frontlines--with destructible environments.

Locust squad leaders could dig E-Holes from which their squad could zerg rush the COG; medics would be Kantuses with a healing AoE chant; there could be manable Siegebeasts; Seeders that act as AA and can jam radio signals for a limited time disabling COG radars (game logic); rideable Beastmounts, Reavers and Brumaks; "hero classes" a la SWBF such as Raam capable of controlling the Kryll, Skorge wielding his dual chainsaw staff, Karn mounting the Shibboleth, Myrrah piloting the Tempest, Ukkon able to command AI hordes, etc. Playing as the Locusts would be similar to Beast mode or Overrun, you mostly play as Drones but can unlock playable Tickers, Wretches, Maulers, Serapedes, Berserkers, Corpsers--the list goes on--if you and your team PTFO.

COG would have access to ground/air transport vehicles like Armadillos and Ravens as well as Silverbacks, Centaurs and Khimeras for fire support; superior firepower with air-droppable power weapons like mulchers, mortars, one-shots and vulcans; squad leaders could coordinate hammer of dawn strikes, artillery and smoke barrages, lightmass bombs that destroy all e-holes and temporarily disable enemy spawning; the engineer class could construct Horde fortifications like barriers, sentries and turrets, but also place sandbags for cover and seal doors; only medics can revive (though downed players can crawl and be dragged/carried by teammates) and they're equipped with stims and stim-gas grenades.

Weapons and characters would be deeply customisable, both cosmetically and functionally as in Tactics. I'd love to see new movement systems (crouching, proning/crawling which you can dive into on your front/side/back, vaulting chest-high walls) and the return of old weapons like the breechshot, booshka, digger and tripwire crossbow. Lambent could play an equaliser role on certain maps. Immulsion grenades would be spicy, toss it at a group of enemies and watch them turn into Lambent, makes for a good distraction but can easily bite you in the ass. Disregarding canon as I already have, maps could take us anywhere. Personally an assault on Nexus beginning with a cinematic grindlift deployment (perhaps allowing squad leaders to choose where their squad deploys) while the Locust prepare their defences would make me cream.

Now if only TC or some other studio could translate this into something that's actually playable.