I think there should be three new independence referendums, in Scotland, Wales, and N. Ireland, and if any or all of them want full independence, they get it.
I don't agree - recent history tells us we should be very careful when we hold referendums. In my view they should only be held under very limited circumstances, specifically:
1. Whether the government of the day wants to make a change.
2. Where that change is of such constitutional significant and, in reality, irreversible in the medium term that the government cannot really rely on their electoral mandate to make that change.
3. Where the change to be implemented is clear and where the government has the authority to enact that change.
Without those criteria being met, you really just have an opinion poll.
What's left of the UK (possibly only England) should then become fully federal, with whichever of of the three countries are left having a regional parliament with the same powers as the Scottish one at the moment (which would mean an upgrade for Wales, whose assembly has fewer powers that Scotland - I don't know about NI), and England being divided into four to six regions, each having a parliament with the same powers as Scotland. The Westminster government would only deal with issues affecting the whole UK (or what's left of it).
Not sure I'd use the term 'federal', but I agree with the notion of regional devolution.
This was actually the plan under Blair - but it got no further than Scotland, Wales, NI and London. It ground to a halt when the North East voted against a regional assembly.
I think the current government would claim they are doing this too, through the concept of the metro-mayors with significant devolved powers. However focussing devolution on cities rather than regions leads to a democratic deficit where certain powers are devolved locally if you live in some places (e.g. Manchester) but not if you live a couple of miles over the boundary in Cheshire.