Removable light weight step:
I haven't seen one in years, but someone used to make a single step that had curves that looped over the tire in a hook shape. The ones I saw the "hooks" were tubing- you could home make out of pipe aluminum. If there is room behind both front and rear tires the two looping over the tire pipes (big upside down hooks) can come togather in the middle behind the tire after a 90 degree bend on each of the two hooks to meet horizontally (lower better-as space allows on the most restrictive of the four tires). The front/step braces against the tire (depending on width of step/platform, might need additional width to span over wheel on tire). You'd probably want to make this step a small platform with room for both feet.
This one step could be used consecutively on each of the four tires to access and clean the snow off the top/roof with a long handled tool.
Your being tall would help this idea work.
If you are camping in snow country when snow might fall, a T brace of the roof on the inside to share the load might be a good preventive measure. Obviously you don't want to "spring" your roof to a permanent concave structure. Wet snow can weigh a LOT!.... As you well know from this experience!
Great thread! I just found it and read it all in the last few days.
If my above description is lacking, pm me and I'll call you and try to explain better in person.
Not as versatile as a ladder, but small and light, and would allow 4 point access to the top.