Ground share with Racing club Warwick would be ideal.
Sadly the road infrastructure and lack of space for parking is an issue. Don't the Old Warwickians play here as well?
The local club that has a ground in a slightly better location is Central Ajax Football Club Warwick (on the same road as Racing Club Warwick, but the other side of the bypass).
I agree the CBS Arena for the short term, using one stand, but my guess is that it would be expensive to rent, and may end up repurposed to something other than an outdoor team sport venue.
The only assets Wasps currently still have available to them is the EPIC site in Henley, so that is where you start from. But, you have to consider you have a lot of fans in the South East, but no possibility of playing anywhere near them, and a lot of fans in South Warwickshire (and some in Coventry). IF Wasps is to survive and move forwards, those elements have to be at the heart of any solution. And I don't see any alternatives, and what I suggested is highly unlikely to happen without (a lot of) money and time.