Just throwing a few random ideas that MIGHT work, dunno yet though.
Ok, so how about 4 independent motors geared super low with wheels attached, then mount that onto a link that can rotate 120* starting with the bottom of the tire at 9 o'clock and allow it to move the 1 o'clock position. Understand me so far? If not, PM me and I'll explain in much greater detail. Anyhoo, back on topic. Each link has its' own shock as do most normal RC crawlers. Ok, very imaginative frame design right here: Esc and such fit inside a "sphere" split into 3 pieces: 2 hemispheres and a lil strip that each hemi secures into. Then, 2 links attach to one hemisphere, the other 2 do the same with the other hemisphere. The 2 hemi's can rotate freely like something with a bearing or something, I dunno, just imagining it in my head. You guys understand what I'm saying so far? Can you picture it? Hopefully you can! Anyhoo, batteries are LiPo, small yet powerful, and they go inside the sphere on one of the pieces. Ok, so if you can imagine what I am, than this would be the ultimate crawler in that it can articulate 360*, each wheel can move 120* so if you dont have a good steady tire on a rock, you can just turn it and bam! Now you do! This would require a very big radio with like 9 channels, so I don't think it's THAT possible, but definately probable. Anyhoo, that's my crazy weird idea for an unlimited crawler. If I had the money, I'd build it and kick some a$$! lol Then sell it for lots! haha chyeah