"Devolution" is a good idea; though with care taken to make sure links are strong and it is not seen as a "division" but as a recognition of "you're much better placed to organise this area of our outreach".

"Wikimedia in Scotland" is a great idea for focusing the brand.

There is no rule that says we have to use a single Wikimedia UK brand, and in the current climate (especially in Scotland) companies are now quite successfully leveraging a Scots targeted sub-brand. If this makes things more palatable north of the border - lets do it :)

Tom