This is exactly what I'm suggesting. Well marked alternate routes with jumps, drops, ladder bridges, etc on the trails that are already in place.I found the skills park the other day at Burns. It looks like it just needs to be ridden. I took a couple laps on it but I was on my cross bike so it was kinda slow. Burns is a short ride from my house and I enjoy the trails. The skills park may be small and run down but at least it's there. It's a start.
Anyway, where I used to live one of my favorite places to ride had both XC and free ride on the same trails. All you gotta do is build an XC trail and then along the way have a jump or drop off to the side. Trail work days consisted of spending most of the day reworking turns, clearing drainages and then a short time building jumps. Over the yeas they've created a nice collection of jumps from easy to kinda terrifying.
I found multiple places on Jackfork where if the trail were a couple feet to either side you could turn a boulder into a jump or drop. These weren't anything crazy...certainly something you could ride a hard tail on.
I have only been there once sometime last year. That place seemed kind of sketchy and looked like nobody rides out there so I haven't returned. I might check it out though if there are some new trail features.There are berms, jumps and rollers popping up at Boyle Park. You might want to check it out.