Previous tests of mine showed that Rei-Six still hangs without the "loader.cxi" and basically still requires all of the files (minus the bootsplashes) provided in the /rei folder. What was removed was the need for the firmware bin files, unless you are using an emuNAND. To confirm this, I went and tested it and it does hang without the loader.cxi*snip
I don't have anything to add to this part at the moment as it seems better suited for Crimson.
Personally as a tester myself I rarely see any situation where keeping such old setups has ever come in handy. Most of the testing I've personally done was for newer setups and never anything older. Although to each their own, maybe you have situations where such setups are necessary. Although I can understand having an nonstandard setup, as my 3DS is literally one of the most nonstandard one can get.