I was able to get my old PSP-1000 to work with RJL .20a.
Not giving the link, sorry. Don't know if its against the rules or not...
For those that want it to work. Be sure that you have a pops.txt, vsh.txt, and game.txt in the seplugins folder.
If you don't have all of them, create them and paste "ms0:/seplugins/RemoteJoyLite.prx 1" to game.txt and vsh.txt.
Paste "flash0:/kd/usb.prx" and "ms0:/seplugins/RemoteJoyLite.prx" into pops.txt.
Save the txt files, Totally shut down your PSP(Holding the switch up), Turn on your PSP while holding the Right Trigger to enter into your recovery menu, Go to Plugins and make sure RemoteJoyLite.prx is enabled.
Exit the recovery menu, Boot up BBCS2, after you make your save file wait til you get to the main screen after the PRESS START screen.
Open RJL. You should have BBCS2 shown on your RJL screen.
Plug in your stick/pad, Right click RJL, Configure the binds with RJL, and enjoy playing with a stick or pad.
SWARROW MOON!
If you can't get it to work after my suggestion there's not much else I can do. I just did what I described and it worked for me.
Forgot to add that Platinum is a very fun character to play. Can't wait to try her out on console.