I hope it's more realistic to crawling than just driving up a smooth canyon wall. I'm quite interested in it. I'm really wanting to see a simulator like VRC but for rock crawling.
I went and pre paid for my copy of the new Baja off road game yesterday, it looks like it's going to be sweet.
Insane was a fantastic game in it's day, great fun to drive and for it's day very realistic suspension dynamics etc. Trouble is that was in 2000 and games have come a LONG way in 8 years. The problem I had as a map maker for Insane was the ability to make small, difficult obstacles was severely limited by the engine because of the power of computers and 3D cards it was deigned to run on. It is possible to make very challenging rock crawling courses but they don't look realistic, because they are all jaggies and triangles, rahter than rock shapes.
Personally, if you want realistic 4x4 action in a build-it-yourself environment hang around for rFactor 2.0. It's going to contain the correct physics for all-solid-axle vehicles (rFactor 1.x only allows 1 solid axle per vehicle). The rest of rFactor already is flexible enough to do the rest but the lack of axle dynamics have push the kosh on any rock crawling mods so far. Trouble is no-one knows when it's gonna be released by ISI and when, or even what it's gonna be called. :\
I'd love to see a good rock crawling sim too, especially one you can mod easily.