So as it turns out, even if this sounds off, this is probably it. If you browse the official store, you can see that some
some Eternal-based products list "© NT/PSEP" on their copyright. (The abbreviation seems to be used randomly though,
other Eternal products do list the full "©武内直子・PNP/劇場版「美少女戦士セーラームーンEternal」 製作委員会" copyright).
So PSEP and PSCP are abbreviations for the Eternal and Cosmos Production Committees, and they're probably based on some Engrishy rendition like Princess Sailor Eternal/Cosmos Planning or something to that effect.