Work against the wall at 2.7 tons.

The U27-4 reaches about 9'5" deep, which covers most residential foundation, drainage, and utility work, plus larger landscaping and septic jobs.
The U27-4 carries Kubota's tight tail swing design at just under 3 tons, which suits contractors who need more digging power than the U17 but still can't have the counterweight swinging out against a wall. The KX030 covers similar ground but with a conventional tail, so it needs more working clearance.
It weighs about 5,700 lb, which is within range for a properly rated tandem-axle trailer and a three-quarter-ton or larger tow vehicle. I'd confirm your specific truck and trailer combination against the actual rating before you commit.
Yes, a hydraulic thumb is a common attachment at this size for grabbing rock, root balls, and debris. I can go over thumb and bucket options once I know the job you're running it on.
For a lot of Grey-Bruce contractors doing septic, waterline, and foundation work, 2.7 tons is a real working size that still trailers easily behind a mid-size truck. If most of your jobs are tight to structures, the tight tail swing here is the reason to pick this over a same-weight conventional machine.
Tell me about your property and the work you need done — I'll point you to the right machine, even if it isn't this one.
Tell me what you're working with