I liked the one-shot, but I don't think they intend to have this serialised. As Shinuki said, it's probably just for the fams and just for their own fun. Shirai probably had an itch to write this story for quite some time, and this was just them letting it out. I bet when they return it'll be...
Shiro would probably be one of the first artists jump would contact if someone who's just a writer brings in a series. But i hope she gets enough rest and recovers completely before she gets back to work
Ao no Hako was really sweet and nice. Don't know how it could be a series though, it's one of those oneshots that really feel like they should stay as one shots, unless the author decides to write a story about the development of their relationship and all
This reminds me that this year we had pretty concerning sudden absences in issues:
1) Magu-chan's MangaPlus having no "next chapter" thing (which was just a false alarm)
2) MHA's sudden disappearance (which was due to the changing of workflow or something)
3) ...and now Act-Age's situation
Honestly, UU imo would safely be categorized together with Mashle. It's one of Jump's better successes recently, and they should just continue promoting it more. (More CPs please)