Well, my biggest appeal to PUP is the potentiality for it to be a tank actually. I do not like our existing tanks. I don't care for heavy armor/weapon job aesthetics in any regard. None of them fit into any of the aesthetics I like in fantasy jobs, but the idea of being a more mystical/whimsical tank does appeal to me and would give me a job in a role that I currently do not play at all in any capacity. What I imagine is creating a pseudo "ranged" tank that shares HP with their Puppet, but can move around and pre-position themselves for mechanics, but comes at the cost of being more technically challenging to pull off correctly. Aesthetically, I could see this taking on either a more mechanical style similar to the mammets we have currently, or go in a different, theatrical type of design--like a kabuki puppet or something along those lines, and the strings that you use to control the puppet are tied to your lifeforce. When you need to dodge mechanics, you have to recall your puppet and snap them back to you.
That's something that I think captures a design space we objectively do not have--that reaper does not encapsulate in the slightest. I think a concept like that would not only appeal to a fair amount of players, but could also draw people who aren't interested in tanks into tanking. One of the issues with tanks and healers aesthetically is they tend to hit many of the same general notes, so someone who's not interested in the heavy armor, big weapon aesthetic of WAR isn't any more likely to be interested in DRK, for example. GBN diverges slightly from that design, but is still a very in-your-face, "heavy" feeling aesthetic. Now, I'm not married to that idea in the sense that if we don't get that I'm quitting XIV or anything, nor do I think that rendition of the concept is likely to be made into a real job in this game, but I do think that's largely unique and interesting in contrast to what we currently have by a long shot.
EDIT: It would seem this concept already exists in a way here in this mobile MOBA:
https://www.youtube.com/watch?v=ATDLd4bUoeM&t=267s