Yoshihiro finally chose to share his method on how to create a loader to run gta:lcs on 1.50 psps, here it is

decrypt all your ~psp and rebuild your iso
download the pspsdk and build your ~PSP decryptor
with the 2.0 PRX and ELF support
you have all you need on psardumper 2a
i not have time for that assuming it will
with DEVHOOK 0.22 because dev hook
not use the game_pluging.prx for load your iso
and iso emulator yes . look when you load your
iso from the psp os with umd emulator
your psp after the white screen
check if your eboot.bin is encrypted and if is not
encrypted you get an error 8002048 :=) .

now download the pspdev sdk and code your loader ;=)

(this is a log from sonyxteam channel)

As he said we do not have time for that, so I suggest another dev team work on this, based on yoshihiro's method.

Please some one check this out i havent got a psp sdk

i'm sure this might be the lead we have been waiting for !!!

Thank you Sonyxteam ( Yoshihiro )
you guys are the best hope you guy will keep hanging around the psp scene for a long time
keep up the great work