I think it should start Bahrain, partner up with Gulf Air.
Why, the Islamabad Airport isn't new enough now, all of a sudden?...
Islamabad not bad option as it would provide another link for people going to USA, Europe, and UK another option to Pakistan. I am sure there is ton of cargo between Europe/UK and Pakistan, and I am sure tons of business folks from Europe/UK that travel to PK as there many commonwealth ties. Delta can also code share on this flight as well, since US government workers have to fly US metal or codeshare flights. Islamabad is safe city, compared to rest of country, and has stability.
Bahrain wouldn't be bad either, as they can codeshare with Gulf Air, Bahrain is financial hub just like London. I am sure Gulf Air also wants more traffic share into the UK to get back with competing levels of EK, TK, and QR. Plus Virgin can send pax via Bahrain to India, Pakistan, Bangladesh, Thailand, Sri Lanka, Middle East/Africa, and Thailand.
I am not sure how Virgin Atlantic mileage is setup, all that. Obviously there future destinations kinda depend on that.
Though Bahrian, Tokyo, Singapore, Islamabad, or another India destination would be nice.