I'd definitely like to see the 8/20 merged, but how would it work?

There is a small turning circle just before Prestbury Road (see here - I think you will need to be on a computer to view it though) where the service could turn around and then head back down Hylton Road to St Annes, where it could pursue the usual 8 route.
Can full size single deckers be used on the 8 though? Some of the estates the 8 goes through in South Hylton are pretty tight, but not much tighter than those in Hill View (and I've seen ALX300s be used on the 10/11 very occasionally).