In retrospect, the sweet spot for the Lib Dems to hit in 2010 was to maximise their seat total whilst still having a Tory majority. Having a more left wing leader like Huhne (or Cable, if the scandal comes out pre-election), who loses more seats to the Tories but partially compensates with seats from Labour, might be the best possible outcome for them. Whether due to election results or his own misdeeds, Huhne would be gone before 2015, and someone more moderate like Clegg could take over and be well placed to take a significant number of seats off of a Conservative government who have had to take the blame for what was likely a more severe form of austerity than they implemented ITTL.
The biggest barrier to that would be fear of the Lib Dems propping up a Labour government also dependent on the SNP. A better result for them at the Holyrood Elections of 2011 might go some way to preventing the nationalist majority and averting the referendum in the first place, but they would be unlikely to be in an especially strong position at that point in the parliament.