imo the smaller size (being able to fit the maximum amount of these into a grid), makes them already very strong
the fact that they also grant 33.3% higher bonuses per tile seems a bit much
even though your equipment grid sizes are on the smaller side and the crafting costs are relatively higher

otherwise great concept, i think i'll keep this mod (though probably with a very strong custom nerf)
maybe there could be a setting to adjust the movement bonus

I can definitely add a setting for the movement speed bonus, shouldn't be an issue.

As for the balancing, I'd have to check this internally, but I believe they still require the same 200kw as a standard pair of exoskeleton legs, so while it's technically possible to put twice as many of them (or more) in a smaller grid, the power demands will generally increase faster than the other equipments can provide (especially when the fission reactor is still a relatively massive 4x4, and only provides enough power for 3.75 engine speed boosters, capping at 75% movement speed bonus, without any other equipments).

The vehicles with larger grids also tend to be a lot heavier, so they would need more speed boosters to achieve the same speed as the lighter vehicles with smaller grids (like car vs tank).

Though tbh, the biggest reason for the smaller 2x2 engine equipment size is because I hate the awkward 4x2 size of the exoskeleton legs that can't be rotated lol.

What a brilliant idea, it should be possible to register a custom rotate keybind and rotate the exoskeletons by replacing to cursor stack by a rotated version.
Regarding the energy consumption, i think the vehicles usually sit idle and rather drain the batteries when used, at least that's how I use them.. but a setting for that would certainly be handy too
I certainly find your engine boosters much more immersive, but i wish there was a 2x4 or 2x3 version (though finding a good graphic for that might be difficult)

An example for a fake rotate keybind would be my universal turret mod

Added settings for both the movement bonus, as well as the power requirement, as of v2.1.9

What a brilliant idea, it should be possible to register a custom rotate keybind and rotate the exoskeletons by replacing to cursor stack by a rotated version

This would be awesome, but I have very little experience with runtime modding; I try to stick to the data-loading phase of the game.

I certainly find your engine boosters much more immersive, but i wish there was a 2x4 or 2x3 version (though finding a good graphic for that might be difficult)

There's a similar 2x4 equipment from the aircraft mod, specifically intended for use with aircraft (which I add compatibility to other aircraft mods), and has a unique graphic too.

Ideally, I would prefer to have a unique graphic for the speed booster, maybe as a 2x3 equipment at the largest, instead of a simple recolored engine unit, but art is not my strong suit either lol.