The service manual for the 540 lists the weight of the 2 post AL540 as 7290lbs with a 165lb operator, Titan HD2000II tires, counterweight, and the rear tires fluid filled. Subtract the operator's weight and you're at 7125. Dave says the HD BMG weighs 380lbs, so that put its weight at 7505lbs. Cab and air adds 330lbs.
So, call it 7500lbs... it wouldn't be that difficult to have a capable trailer that weighs under 2500lbs keeping you under CDL. The 540 without an attachment is 149" long (12' 5").
Justin, did you figure out the height required?
According to the service manual:
The pins are 8" off the ground with the arms lowered
The 540 has 120"/10'/3.05m of height to the raised bucket pins.
Using the specs dirt/construction bucket:
35* of rollback/45* dump at full height
17.5" of dump reach at full height
142" max reach height
All that to say... with a high dump/roll out bucket, you can add at least 1.5' to the bucket pin height, likely more, and still have good reach and excellent dump angle.