I doubt there was ever any chance of Virgin successfully continuing any operation of Concorde; it would have required the wholehearted cooperation of BA, and that was never on the cards! Air France were, I believe, adamant that no-one would ever operate their Concordes once they were retired by AF, so that was a non-starter. How much research and negotiation was done on the Design Authority issue, I've no idea.
However, had there been the will within BA and the Government to see the aeroplane continue to fly without any commercial risk to BA itself, I don't see why an engineering support package couldn't have been negotiated. There has been much cooperation between Virgin and BA in engineering and other support services over the years and, away from the headlines, the two companies are quite capable of working together when it suits them to do so.
Lastly, while the publicity opportunities were too good to miss for RB, his enthusiasm for Concorde, both as an engineering achievement and a commercial tool, is quite genuine. I'm not sure there were that many - especially on the financial side - within Virgin who were as keen as he was to see it in our colours as he was, however!