"PSone Loader is a software which allows you to run PSone classic games from the PS Vita Livearea (custom PSone bubbles). It does support custom as well as official PSone games. This software is made of 3 components: The DUMPER, which does dump the PSP and KIRK headers of the 'simple' module (DATA.PSP) that is required for the SIGNER program. The SIGNER, which does inject the fake signed custom 'simple' module into a PSone game converted as 'EBOOT.PBP'. The LOADER, which does patch the pops module in order to allow custom converted PSone games and to bypass license verification of offical PSone games."
https://bitbucket.org/TheOfficialFloW/psoneloader/downloads
This should support firmwares 3.00 to 3.52. Rejuvenate is recommended to make the process easier but not required.
I've not had chance to test it out yet, but I'll probably stick with TN-X on 3.18 for the time being. This is excellent work by TheFlow, but it does look like one game per bubble rather than a loader. Should be great once this develops, though!