A Progressive Alliance sounds good to me. Not sure how it would work with FPTP, but at this stage anything is worth a try.
I could see Labour turning its nose up at it though. Especially Corbyn's version of Labour.
Ideas of how it could work: perhaps not trying to split the vote by standing candidates against each other in certain seats. Sharing resources (man power). Finding common goals and interests.
It depends on how smart Labour are at the moment. They CAN NOT win a general election at the moment. It just is not possible. They could use this as breathing space to reconnect with their grass roots and build from that (which is frankly what they need to do).
I think there is a lot in it, but also a lot of problems.
Right now though I do think that there is a public mood across political boundaries where people want unity, they want consensus and frankly they just want less of the bullshit we've had for the last 4 months.
"WE THE PEOPLE ARE FUCKED OFF"
we need to work on some catchphrases and some passionate stuff of our own don't we? And humour. Definitely some humour in order. Humour goes viral just as much as controversy