I got back three interesting ideas. The below in italics is exactly how it came out after I had steered it in a direction towards new ideas rather than rehashing existing ideas. I only have a basic account so could not produce pictures, but it does offer an idea in how they'd look. Obviously DE would want to carefully craft a frame to make them suit the game and have synergies between abilities and mods, so these might not work in the game, but they're fun to imagine:
1 - Certainly! Let's imagine a Warframe designed with a commando theme. We'll call this Warframe "Commandera."
I think this sounds very cool but I would still make a few changes. I think the stealth ability should work as a togglable whenever you stand still for more than a few seconds, but cancel when you move, and giving you an execute option for near-passing enemies. The passive could be more unique, like being able to equip two primaries or two secondaries, instead of one of each. They'd share ammo, but you'd get double the normal max ammo cap. The 2, 3 and 4 abilities however sound amazing.
2 - Certainly! Let's envision a Warframe with a spider theme, and we'll call this Warframe "Arachnox."
This one seems really cool too. Some elements seem already in the game, but in this example, the dome and zip-line could be used more as a way for creating paths to funnel enemies in certain ways, rather than being too similar to Frost and Valkyr's abilities.
3 - Certainly! Let's imagine a Warframe with a swarm-like theme, and we'll call this Warframe "Aetherium."
This one seems so cool too. Especially the third ability, but if you literally encased another player, so that they were in control of where to go, but you are helping them with dmg mitigation, while also being able to shoot independently of your ally - like as an additional pair of arms, shooting or swinging at passing enemies. Imagine a super-tanky, double-Mesa!
Anyway, apologies if this just created a yearning for something impossible in Warframe - just couldn't help marvel at these ideas on my own, if only to imagine playing as them.