Peter Franklin strikes again:
"Devoting a Cabinet minister to financial stability is no guarantee of financial stability, but it would help and, if nothing else, would send a message to the anxious savers and pension fund holders of Middle England that we take their concerns seriously."
At the moment no one has direct overall responsibility for financial stability. I think that just about the only way you could make things worse is to put a politician in charge. This isn't an area where there are many ideological issues at stake that should be decided democratically. It is, instead, an area that requires expert and experienced judgement.
Your ideal person to put in charge of financial stability is someone respected by the markets with a real knowledge of economics and how the system works. A non-politician. Make it a ministerial post and you're highly unlikely to wind up with someone qualified to oversee the financial system (of course the same can be true with the Civil Service - see Sir John Gieve). There aren't really people with those kinds of qualifications in the Commons - just a few ex-financial journalists and the odd banker.
You'll probably get someone who won't have real experience in anything but politics. Particularly given that it will be a job where people only notice the minister if things go wrong. Just like the Home Office at the moment it will be a poisoned chalice which will mean it won't even get the brightest ministers. Whoever got the job would just have to watch, fearfully, and hope things take care of themselves. If something went wrong there would probably be a carefully established media strategy but little idea of what to actually do about the problem. The stability of the British financial system would be further impaired and Middle England wouldn't be impressed.