Nice, I really like some of the ideas in this thread! I do agree that it's unlikely to be common in the BT universe, but it's still awesome stuff for a campaign where that 1 in a 1000 instance happens. And hey, if it's cool to the GM and players, have it be common.
Which gives ME another idea. I can see a city/colony being laid out by urban planners where they expected people to move about in tiny, 10-ton mechs. Perhaps it was founded at the dawn of the 'mech era in a misguided anticipation that the new technology would render all other vehicles obsolete. Maybe it was built by an eccentric mega-trillionaire who just loved mechs. Who cares why. At any rate, such a place with common mech-taxis could also give us:
That one's hilarious. =)
Check out the Celerity for some ideas. (XTR Comstar)
How about deep sea fisher? Even without UMU, I could see them trotting around the bottom of an ocean or lake looking for critters that dwell there, or for stuff like pearls or their alien equivalent.
I also haven't seen pest control mentioned.
A broader idea: a lot of things are the size they are because of the need to repair or replace them later. In many cases, you can scale that quite a bit without difficulty. Sometimes, the bottleneck is the human hand.
How about macro-scaling things like water and sewage plants, even some building maintenance items? 'Mech sized light bulb replacement, HVAC, etc, the 'Mech sized building engineer.
I'm sure there's other 'macro' ideas I haven't pondered yet.
Paul