Best of luck with the job search Amos. Think it will be tough to get a specific MTB-related job with the seven stanes - best way of working within mountain biking is probably just to get something going yourself.
I live in Edinburgh, so it's actually harder for me to say what opportunities there are around the scene here. I drive to Glentress, ride, and go home - don't really experience stuff like rentals / bike shops / B and B / eating and drinking etc, all the stuff I would do if I was going on a riding weekend further afield. The best bet would be to move to Edinburgh with a regular job lined up, go riding for 6 months every spare minute of the day, and see if there's any angles to get involved in MTBing.
One thing to bear in mind is that the 7 stanes doesn't appear to be some sort of massive, constantly evolving project with a significant workforce. I don't know anything about how the 7stanes are managed, but just from riding the trails it seems that places like the Tweed valley have the resources / aspirations to be MTB centres / parks with ideas for development. Other centres seem less resourced, more like 'we've built it, and we'll drag off the occasional fallen tree, but that's pretty much it.' Happy to be corrected if that is not the case, just my impression from riding places like Mabie.