Any public facing service that other (services) depend on should not be running on a public IP (especially ones that translate addresses, and ones you have to manually update).
You could run an authoritative NS "hidden" where only your secondary NS can reach out to for zone transfers. You could also escape having a public IP if you configure rsync or scripts to update secodary host files on every IP change.
Thank you! What would such a competitive amount would be? 2 per each region covering east and west? or something more distributed such as 1 in a radius of 1,000km?
Regarding the original post, yours seems a commercial case, which probably will not be supported at the start.