The interesting thing is that the Labour comeback has been distributed oddly. In some seats their vote share actually fell, the SNP just fell more. I think they were something like 2500 votes away from 40 seats.
I'd have to recheck but I'm not sure if that would be the most efficient contortion. They seem to have held on pretty well in Glasgow, etc, with more losses coming from the North East and Borders.
While obviously from a leftist perspective defining the SNP as "centre" and having a leftier-alternative is preferable to making the SNP your "radical" wing, it would seem to involve less contortion to create a new centre-right nationalist party. (Of course this entails the risk of spiralling into a celtic-tiger memefest.)
The problem is that in Scotland even this isn't entirely certain, with Scottish Labour still a very Blairite sort of establishment. (Still haven't really looked into the new MPs who might change that, but certainly institutionally little has had time to change.) There's still a strong case that when you really get down to it, the SNP are the leftiest option in Scotland.
If I really cared to press the point, I could probably assemble an argument that Ruth Davidson is left of Tony Blair.
Also, the UK has a track record of disappointment. You can't verifiably prove that we're not in a 1974 situation here - i.e. the left appear to be surging (Indeed, Benn had huge influence on the 1974 manifestos.) and the Scottish Nationalists are playing closer to the centre, but in reality we're all 5 years away from the biggest kick in the teeth in political history. In 1974 you're spooked by nationalism while most of England stands in solidarity with the miners, in 1977 we've got to defend Labour because they're the best we can get, in 1979 we're all dead.
Just because things are good now doesn't provide any justification for the basis of the long-term decision on independence. Rejecting that just because the UK can cater to short-term interests is absolutely insane. Fucking hell, even the "selfishness" of the 1970s oil argument doesn't compare to what we eventually happened to the oil wealth in the UK:
IT WAS PRIVATISED
I'm still unspeakably angry about this. You can only pull it out of the ground once and we pissed it away. The UK was handed a lifeline by god and it threw it away. If Scotland had fucked off and Nauru'd the lot, even that would have been preferable because England would've been spared the upward pressure on the value of the pound to some degree (i.e. mildly helping manufacturing), but no.
That's of course not even to mention the benefits that come from breaking up Britain as an abstract entity, forcing a re-appraisal of the rUK's place in the world.