In our adversarial parliamentary system you make a decent point. If and I still think it is a big if Labour get 450 seats as predicted then the other 200 would possibly have to form a coalition of opposition led by the second biggest party whoever that maybe, it might even be the Lib Dems if the Tories do collapse completely. I am sure Galloway would welcome that, but would a Lib Dem or Tory or even SNP led opposition offer him an opposition portfolio. I doubt any of them would welcome Farage and he would be a gob on a stick backbencher with next to no influence.
In theory though we could end up with an opposition front bench that included Ed Davey, whichever Tory senior Tory minister survives, Galloway, Corbyn, Flynn from the SNP (I rate him) someone from the DUP, Greens and Plaid just so that opposition roles could be filled.
Whatever happens it is going to be interesting to see how it pans out.