Would it be too much to ask to have a speed running category dedicated to runs done with a single unit? This is something I have been doing since I bought the game last year and I feel like it's a good challenge for dedicated runners.

Whether or not a category is added is based almost solely on its popularity. I can't entertain every idea everyone has unfortunately. If you can find enough runners to run the category enough for some legitimate competition, however, I don't see why not.