Good points. I'm a long time zumo user and made the same assessments some time ago regarding Topo use. Since I rarely do trail riding on my HP2, topo's have not been a priority for on-GPS maps. I do occasionally use them in planning my dirt rides.
Maybe the Garmin Montana will be a better fit. Good luck in your search.
By the way, do some more searching, there was someone here who did/does use a Baja 5 off-road.