There seems to be some confusion here. The Liberals were an anti-socialist party, and ultimately happily joined the national government on that basis. If they swung they other way they would have steadily lost supprt to the Conservatives.
If anything I see a Lib-Con arrangement as more likely - both parties would be weakened and would eventually realise that no gain was to be had in splitting the middle-class vote.
This was what eventually happened in the 30s, this way it might be on more even, or even Liberal-dominated terms.
But until MacDonald too control of the Labour Party in 1923, the Labour Party primarily saw itself as a pressure group rather than an entity in its own right. JR Clynes, or my gut tells me, would carry on this tradition. The Liberals would be pragmatic enough to work with them. The Liberals might have been an anti-socialist party at the time in question but like New Labour, they could drop the "s" word.
I think a Lib/Con pact would be disasterous at this time - it would affirm to the socialist/Marxists in the Labour party that class war was indeed in full swing and could even lead to mass protests, violent strikes and perhaps further action.