I wonder if "prevnext" is the same as pagination? Would there be a reason to map them differently? If you have say the next and previous buttons on the side of a Kindle, they're still pagination controls in my mind, just a more compact form.
I can certainly see a use case for the external one. The MS sites for example have the global MS header (with a bunch of navigation links) and the site header that includes the nav for that site itself. Being able to skip the "network" nav would be nice usability benefit.
for attribute proposal is interesting. HTML also uses different attributes, like there was a
menu attribute for button type="menu" to link it to the menu element, and datalist uses
list. Not sure if this is adding more complexity though? You can also still use aria-label if need to add more context if you have multiple of the same type. I'm in two minds if I think the dots on sliders are pagination or just a sub part of a slideshow component. I've never marked them up that way, but the markup and semantics are fairly similar. But you could kind of argue tabs were pagination too.