One thing you don't see in a lot of traditional grid-based roguelikes is multi-tile units. Most such games are designed on the "one space, one entity" principle (though X@COM has had multi-tile units for a couple years).
This makes things simpler from both a tactical and implementation perspective, but somewhat reduces realism when your fighter '@' is up against a dragon 'D' that should be many times your size, but isn't and can squeeze through any corridor you can. Or in the case of Cogmind, you're fighting (or more likely running from) a Behemoth class robot which, aside from being a capital letter 'B', is still not all that huge compared to a little Swarmer class 's'.
For the 7DRL prototype, multi-tile units were removed from the engine to avoid complications from a feature that wouldn't see much use given limited development time.
Now I've added them back because they'll be fun and further improve variety.
This of course re-introduces level design issues that uniform unit sizes manage to avoid, but large units will be fairly rare so it isn't a problem, and the rarity serves to further enhance their "wow-factor."
In ASCII mode large units simply repeat their symbol across their area:
Right now you're not thinking "wow", but you will when you know what that thing is armed with as you consider the nearest path down which it can't follow you!
Larger than 2x2 is possible, but robots that big would need their own special area to make sure they didn't have to smash through walls to get where they're going.
Large units are also compatible with sprite mode:
Wanted: Pixel artist.
So the days of tiny Behemoths is over. Another candidate for largification is the optional end boss. (I say "optional" because Cogmind should technically be winnable by stealthily avoiding as many enemies as possible, including the end boss.)
Next: Time to spruce up the environment with some "furnishings" appropriate for a world of robots.