How magnanimous of him. I understand it though, I'm prepared, like millions of others, to possibly take a hit via Brexit if it gets us out of the E-USSR's clutches.
I think those who would be happy with the above (unworkable) 3-way coalition you describe are severely deluded. So the price would be a second IndyRef. Scotland leaves, those Scottish MP's won't sit in Westminster afterwards. So even if this nightmare scenario of senile Corbyn the Marxist, Brexit denier Swindleson and wee Jimmy Krankie came to pass, they would end up as a minority govt. again, so we are back to square one. Then you'll have permanent Tory administrations as England returns an average of 300+ Con MP's each election. Of course, that's assuming they don't fall out first when Labour refuses the IndyRef, then won't revoke Article 50 and then gappy will ride off into the sunset in a strop.
I assume your suggestion is tongue-in-cheek about this coalition, as only those needing certifying would ever want it, or be insane enough to believe it'd work.