While I know this is pretty much impossible due to David Cameron probably not having the political courage necessary to sack his best friend as chancellor and replace him with a man who is hated by his backbenchers, I'd still like to present the following list of reasons why Vince Cable should take over as chancellor:
1. Vince knows what he's doing
Specifically, he predicted the financial crisis years in advance and warned of the dangers of deregulation at the same time that Osborne was calling for even more deregulation - in addition to which, Cable's been leading the call within government for the kind of radical action (big infrastructure investment, creating more training and apprenticeship programs, economic stimulus directly for the economy rather than for the banks, etc.) that most leading economists have started to call for - if you look at the recent recommendations in the IMF report you'll see that they're advocating pretty much the same things that Vince has been calling for.
And, I highly doubt that Vince would have produced the kind of "omnishambles" budget that Osborne did - something which drastically increased the number of people viewing the government as incompetent.
2. Vince is popular
In a recent poll of the popularity of possible replacement chancellors, Vince Cable came top with 22% favouring him as opposed to the 16% favouring the second place William Hague - given that Cable is generally fairly popular with the public, far more so than Osborne at any rate, making him chancellor could well stabilise the government's falling trustworthiness ratings on the economy.
3. It would show that Cameron is a decisive Prime Minister
Let's face it, Cameron replacing Osborne with Cable would be problematic for him on several levels - it would irritate the hell out of his tory backbenchers (Vince is consistently rated the most unpopular government minister in polls of tory members) and would mean betraying his best friend. But, while this would cause him a lot of problems in the tory party, it would probably increase the number of people rating Cameron as decisive and show that the government was prepared to take radical action. And, if the coalition's decisiveness and economic credibility ratings started to rise, it's quite likely that Cameron would find a lot of his problems with his backbenchers disappear - put bluntly, the tory party (and most political parties in general) will put up with almost anything from their leader as long as they're doing well in the polls.
4. It would give the tories a full-time strategist
One of the biggest criticisms of Osborne, even amongst tories, has been that he's effectively a part-time chancellor as he's also meant to be running the tory party's overall political strategy - with the result that he doesn't have enough time to devote to either job. While Osborne would be very unlikely to want to continue being strategist after being stabbed in the back, one of the main consequences of replacing Osborne as chancellor would be that Cameron would be able to get a full time strategist - something that his party's been sorely lacking as is obvious by the recent lack of any kind of coherent vision from the tories as to what kind of country they want to create.
5. It would let the tories get something from the Lib Dems in return
Getting one of our people as chancellor would obviously be seen as a big coup for the Lib Dems. The chancellor is one of the great offices of state and, as a result, would mean that we'd have to give something up in return. Some tories might look at something like dropping gay marriage or dropping lords reform or having an EU referendum but I think that in reality they'd be more likely to settle with losing Lib Dems from the cabinet instead.
For example, without a hostile Osborne trying to scupper every green measure that comes up, Lib Dems would probably be willing to relinquish the Department of Energy and Climate Change in favour of Ed Davey's tory deputy. Having a tory in charge of energy would soothe a lot of the anti-green tory right whilst also not being too unpalatable to Lib Dems as they'd know that Ed Davey's deputy is actually fairly sensible on green issues and that, with the chancellorship in their hands, they could use that position to continue to enact green measures.
And Cable's former department (Business, Industry and Skills), of course, would also be up for grabs and could quite easily go to either a tory or to a tory-palatable Lib Dem such as David Laws. It would also mean that William Hague would probably be moved from being Foreign Minister to First Secretary to the Treasury, letting a new rising tory star to take over at the Foreign Office and that Cameron would be in a better position to ditch Ken Clarke (who is popular with the Lib Dems but unpopular with tory backbenchers) in favour of someone more to the liking of the tory right.
Some combination of the above, therefore, would probably give the tories back as much influence as they had lost whilst also, and crucially, giving Cameron plenty of ministerial slots to use to shore up support amongst for his leadership amongst the tory grassroots.
Of course in reality Cameron will probably keep Osborne in place to the economic detriment of us all and with negative effects on the government's credibility instead of replacing him with Cable, but a man can dream can't he?