If you believe Scots are sponging incompetents, then it would not be bad, in fact at least in theory good, for England. If you think they are inherently as capable as the people of Monaco, Andorra, Liechtenstein, Iceland, Luxembourg, Norway, Denmark, Switzerland, Belgium and Netherlands then they would be certain to survive, probably quite well, on their own. If they are as capable as the average of the above then losing them from a UK beset with socio-economic crises would not be good news, if you assume maintaining the UK's existence is desirable. As for how they would survive, all they need do is copy the plentiful examples of ways to do better than the UK.
If Shetland really wants independence then it should, and I believe will (in time), get it, just as Scotland will if it wants it. The evidence of a determined will in that direction is what counts.
My opinion (which I realise does not count) is that independence would be good for both Scotland and England, including in ways never discussed in the presence of the emotional porridge that usually dominates.