a 2nd potential solution

A second potential market solution would be for a group of ISPs with common
interests to join forces and apply for a suitably sized CIDR block directly
from the IANA.

In this scenario, the ISPs would not be using "provider dependent (AKA PA)"
space, but rather PI space.

This same group of ISPs with common interests then would issue an RFP for a
"group buy" and then select 2 or 3 NSPs to carry their traffic through the
normal commercial negotiations process.  Because the ISPs were allocated PI
space out of the same address block, aggregation would be possible and likely.