a.) then how would a new or offline IPIP station connect if AMPRGW were DOWN at the time?

This is not a task of AMPRGR but of portal.ampr.org

b.) then how do I get routes from AMPRNet without a DIRECT CONNECTION tunl0 connection to AMPRGW?

As I wrote is is possible to deploy a second system that does the RIP announcements

c.) what if I can directly reach 2 or more AMPR subnets (but not the Internet)?

We already have a large network of radiolinks running here in Europe, and I think also in some other areas of the world. It does not rely much on the internet, except for DNS. I download the ampr.org DNS zonefile daily so I have it available when we are offline.

a.) AMPRGW is currently the only route announcer (but you address that elsewhere)

I think it is important because it is the only weak spot I can see.

b.) Next, it's not the ideal route to all subnets

Why not?

c.) this solution addresses the possibility of redundancy to other subnets, as well as AMPRGW

I don't understand. There already is full redundancy. We have a full mesh.

In planning, it would probably be an alternative to IPIP, and not a replacement. Ideally, there could be a few regional gateways, other stations connecting to one or more regional gateway and to other end-user gateways.

That is how we run the network here. What is your proposed change?

Rob