Another possibility is the OneWorld VisitAsia pass, but unfortunately many of the cities you list in Asia are not served by OneWorld airlines (or only from long haul which means taking other means either in or out), including Dhaka, Angkor, Shanghai, Xian, Agra, Bangalore, Jaipur, Okinawa, Kathmandu, Da Nang. Note also that there are limitations on having Malta and Moscow on the same OWE (you would have to get to Moscow from somewhere other than the UK, e.g. HEL).

Of course many of these are doable by other routes (e.g. the Delhi Agra Jaipur triangle by train is by far the best way IMO)

To visit all those places looks like it would need 3-4 months on the road to do it properly... is that what you had in mind? Otherwise I would strongly recommend splitting it all up a bit.