Yeah, I’m wondering about that: Is it possible for a package to detect whether it is being used/imported in the REPL or inside another package? If that’s possible, UseAll could print a big warning if it is being used in another package. In that case, I would say: Go ahead with registering it.
[P.S.: I’ve spun that question into a separate thread: Can a package detect whether it was imported in the REPL vs inside another package?]
Either way, I’m not strongly opposed to it being registered. But I’d also point out that registration in the General registry isn’t may quite as important as people often make it out to be, and, since we have the requirement that registered packages can only depend on other registered packages, not being registered is good way to enforce it being a REPL-only tool.