What would happen to Scottish MP's/MEP's/Councillors in English/Welsh seats (and Vica Versa!)?
I know Irish people can stand for election in the UK, would it remain like that? Would Scots living in RestofUK be elidgible for citizenship?
No doubt they would. I've not heard anything to the contrary. Citizenship, IIRC would be open for those living in Scotland with existing UK citizenship, which makes sense. Those who were born in Scotland but live elsewhere would be able to apply.
You only have to be a commonwealth or EU citizen to vote in local, Welsh, Northern Irish, and European elections and Scotland would almost certainly remain an EU member. Likewise if you are a commonwealth citizen you can vote in British elections so as long as Scotland was a commonwealth member one could still vote. I know as a Canadian I would be able to vote if I lived in Britain. Likewise while Scotland can set its own voting rules and own nationality rules, EU law requires that all EU Citizens be permitted to vote in both European and local elections, although not required for national ones. They also might just set a minimum residency period too as I believe in Holland and Denmark one can vote in local elections regardless of citizenship if they have resided in the country for a certain number of years.