10 years ago - yes, but today with $0.6-1.0 per watt the panels are not likely to be stolen. Especially, when it takes some sweat with couple dozen screws. 2-3 screws per bracket, 4 brackets per panel. Panels are bulky, heavy and difficult to sell. Roof rack fittings like Thule or Yakima saddles for kayaks, bikes etc are MUCH more likely to get stolen.
I've mounted my panels on RV (not on the toad) with rivet-nuts embedded into panel (Golden HVAC's idea, and I like the convenience of use) - and with tamper resistant screws, since I spend a lot of time in Mexico. Then I forgot that "tricky" allen key at home, and needed to remove one panel to do some work. The nearest auto-parts store in a mid-size Mexican town had those allen keys in stock. Unless you are going for REALLY rare tamper-resistant heads for $6 each, and $40 driver, you are no better than with usual Philips heads.
Hpdrver - yes, sort of a portable system that uses roof rack as a stand. You will still have some cable-routing pains when getting the cable from controller through the RV wall or floor or storage lid to the outside. Nothing impossible. If your RV batteries are outside, then there is already some hole for wires from batteries to the inside.
Allow few degrees slope on the panel to shed the dust and rain water - probably towards the front of the car.
I think the very 1st post on the Finished Installs list is by Sleepy, she installed panels on the roof rack - though on motor home, not on toad.
Here. Doesn't have to be these exactly panels - the post is old, prices are much lower now, many sources for panels and controllers.