Debug Firmwares 1.00 and 1.50 are available for download for a some time and AFAIK pre-1.51 firmwares allow to run ELFs directly, to install retail packages, to decrypt retail EBOOTs and so on. However I faced a major problem with those firmwares - there are no tools (like ftp-server) to exploit its possibilities.
All the public-released tools (that I can find) have been created with 1.92 SDK at least so they don't run under 1.50 firmware. Also I didn't see any SDK prior 160.008 in a wild i.e. it's unable to compile own tools for the 1.50 firmware. Are there any tools available?