I realize this is the MTB project, but I think there are enough people without full suspension that would like to know if the easier trails are going to doable for them. Cyclocross bikes are getting pretty popular and can take on most of the green-blue rated trails, but it's hard to tell when suspension is going to truly be a requirement with surprise unavoidable drops into rock gardens on an otherwise smooth trail. Could there simply be an additional button when rating the trail to say "non suspension bikes are a possibility on this trail" so people with hardtails or cyclocross/gravel bikes can gauge how hard the trail would be for them? Or just a rock rating "30% rocky" etc.
Or maybe even there's enough cyclocross popularity these days for a "CX Project"? ;)
This is a cool idea. Like you mentioned, CX is unique, but there's some obvious overlap with MTB through the trails that each group uses. I've logged this suggestion to be discussed moving forward, but we're a small team and adding another Project is currently unlikely. I like your specific ideas surrounding smaller changes that incorporate a checkbox or some acknowledgment on current MTBP trail pages. More to come!