Not all forestry commision land is FC. Some may be private and managed by the FC.
Expect 2-3 years for permission, setbacks, re applications for funding, re appling for different funding should plans change.
You could try working alongside a local access forum. They have retired people working for them, it can be pretty much a full time job just doing the admin. My folks have been working for three years on a long distance footpath. It already exists to some extent. But to market it and link it up require all sorts of guff. They have been refused access for one section. A reroute requires a new 16 page form to be filled in and another consultation document produced. and another funding app. they cant use the original one….plans changed see?!
But
I also would not get too excited about another "stanes" project. I have a FC chum who admits that the seven stanes created a bit of a monster for the FC that they can almost cope with at the moment but any more would start causing them problems. He doesn't reckon there will be any new trails for a long time yet and we'll have to take what wur gied.
Good luck.