That kind of depends on the Unionist parties now. The SNP already voluntarily abstain from votes that don't have an impact on Scotland, and of course independence would have solved that problem in a very complete way! Within the UK, it will be difficult (impossible?) to find a solution that doesn't short-change someone - because sometimes there will be a legitimate Scottish interest. For example, decisions taken in England and Wales can affect funding for distinctive Scottish policies through Barnett consequentials.