Yes, a 44 BGP network would do the trick, but I am certainly not willing to pay hundreds of USD per month for such an endeavor. BGP peering is not cheap and not readily available in the whole wide world unless it is not piggy backed on another preexisting AS for a select few working in the network business.
Aside from the discussion "what it really costs", this is one reason why I think the deployment of access routers around the world should be coordinated by ARDC instead of being an individual effort by hams around the world each serving only their local region. Certainly there should be room for that, but it should not be the only option.
ARDC can investigate and find one or more VPS providers where they can order a number of VPS including BGP announcement of a subnet at several datacenters, for some fixed price which should be within the ARDC budget.
In the network structure as I see it, there would be routers connected by tunnels and serving a VPN service for the users, but they would not all need to have BGP announced subnets. When it is too expensive to have that in some country, that can be done in a nearby country instead. The private-AS internal BGP routing of all AMPRnet addresses will handle that.
Of course one usually would want a country subnet to be announced somewhere nearby, to reduce latency for the users not connected to AMPRnet. With a well-connected router mesh in good datacenters, the latency will be in the millisecond region, and not like the values we now see for traffic going via amprgw.
Rob