"AV means more coalitions, permanent involvement in government by the Lib Dems,"

Not a given surely! Even within Britain there have been other recent examples. The SNP are just coming to an end of a minority administration at Holyrood. No coalition was formed. The politicians of all parties simply got on with the job and though the SNP were unable to go ahead with some of their policies because they couldn't gain the support from any of the other parties (most obviously the independence referendum)in general the term ran smoothly with the chamber voting on issue by issue. The other parties didn't try to bring the Executive down at every turn. It is kind of possible for politicians to work a bit with each other.