"I always love comments about tarmacing the country side"
As has been suggested such comments often come from horse riders. I can't pretend I understand the needs of horse owners/users, but in many ways their concerns are similar to cyclists in terms of places it's allowed/possible to ride.
In general, in Scotland, it's now possible to walk/ride "responsibly" almost anywhere.
There are places where horses are banned and even places where horses are allowed and bikes not allowed - bridle path in The Braids.
Some bike riders don't take enough care around horses - but some aren't that bothered about pedestrians either...
There's probably scope for more co-operation between horse and bike riders to get better routes/access - but 'we don't like tarmac' attitudes don't help.
Horse interests were actively involved (with other groups) to try to stop the Dalkeith bypass slicing through Dalkeith Park. Not sure if they got any concessions - the opportunity to improve conditions and create links/routes for cyclists was comprehensively ignored.
Historically Midlothian Council hasn't taken that much interest in cycling, but at least this new route shows some interest.
The Council is planning to make the Loanhead to Straiton Pond section of the former Bilston Glen line into a path (presumably with tarmac!)
This is important because the existence of a (working) railway meant that an underpass was created when the bypass was built. The bypass is a real barrier to safe/pleasant travel between Edinburgh and Midlothian by walkers, cyclists and horse riders.
Midlothian is fairly keen to encourage tourism. A good link from Edinburgh for non-motorised travellers would help. It could promote itself as "the place to ride". There are plenty of quiet roads and most of The Pentlands is in Midlothian.
No doubt there are lots of places to ride horses too - perhaps there should be more (with or without tarmac).
One problem is that the bypass is also mostly the boundary between Edinburgh and Midlothian. City of Edinburgh Council is not keen on creating cross-boundary cycle routes because it considers that it's not 'value for money' due to the relatively small number of people that would use it compared with (for instance) MMW.
All the more reason for some joined-up-policies on transport and tourism that don't stop at artificial borders.