I also think the SNP would happily vote for an election. So maybe the Tories, the Lib Dems who have nothing to lose ...
I agree on the LibDems - they really have nothing to lose, and everything to gain.
I disagree on the SNP for a variety of reasons. Even if they might outwardly say 'bring it on' I don't think as a party, nor as individual MPs they'd really be in favour.
First, don't forget they currently hold 56 out of a possible 59, so they have very, very little to gain (max 3 seats) and an awful lot potentially to lose. In card playing parlance at that level you would definitely 'stick' rather than 'twist'. Also of the 3 seats they don't hold I think only one would be realistically a target - I don't think they'd be likely to take the final LibDem seat if they didn't take at their high point and the LibDems low point. Likewise on the Dumfries Tory seat (one I know rather well) - don't forget this was an area with a high leave vote and that will pile on the tory. The converse is that a recovery of the LibDems brings some very marginal SNP-held seats easily back into play for the LibDems, likewise the resurgence of the tories will make some other SNP seats vulnerable, particularly if the remain vote is split three ways (SNP, Labour and LibDem) while the leave vote is effectively mopped up by the tories alone.
There is also the personal issue - remember it is individual MPs who have to vote. The SNP have a huge number of brand new MPs, all likely wanting to make a career in politics, and a fair few in seats where a not unrealistic swing-back means they lose their seats. Do you really think they's want to risk ending up as an MP for less than 2 years, almost certainly never likely to get another chance. Nope I think they'll desperately want to hold on for a full 5 years giving them time to build a personal support.
There is a final point, and this actually affects all parties, but most significantly the SNP. Fighting elections costs money and I'm not sure the SNP in particular can afford it given that they have had hugely significant votes for them in 2014 (referendum), 2015 (general election), 2016 (Scottish parliament and referendum).