since the Hopper was introduced, Gridmap has received an update for some crawling sections. my suggestion/idea is to modify ECA with a crawling section (there are alot of trails on the east coast states) and with WCA coming soon, i believe there should be some trails for us to explore since there is apparently alot of trails in california.
Actually, at ECA there is probably more of those crawling places than on other maps, not always easy to find though, but as nothing stops one to drive trough a forest, that place is incredible for offroading. Follow the coastline, use smaller roads and if it looks like you can make it to waterline, try it, you can find a lots of places to crawl, from highway spawn, left side of the road, to both directions is what to look for, if you drive slowly along the road, you can spot places that at first look don't look nothing but a cliff, but when you drive bit around you can figure out how to crawl there, it is like in reality, perhaps not all are purpose built areas, but crawling place is there where is some rocks:
The WCA map is based on rather the actual coast, instead of the inner cali. So i dont think that there will be rock crawling routes.