Can't we just add the 3.60 nprdm keys to the tools we already have and make eboots for 3.55?
No, npdrm keys aren't for retail games but for psn games or update patches. In addition you have to modify the tools because the algorithm of encryption is different. I don't know this algo, so I can help, sorry.
I bet changing a few things in KaKaRoToKS Script to make from an OFW a CFW could lead to 3.6 CFW. But I'm not sure since I don't have the scripts and the files anymore. But I think that somebody already had the same idea then me, and is already trying.