I think there's a STRONG advantage to keeping things in the program (ala "set") and not outside (ala env variables and command line switches). Right now there's a WONDERFUL bit of beauty in that a bB program is self-contained...you can cut and paste and go. Not only would external controls spoil that, but it's just one more thing to provoke dozens of "I tried to compile this but it doesn't work", like [stella] would get with the "-f3" argument DASM usually needs...(gee, who would miss that? *whistles tunelessly*)
The set syntax seems very reasonable. There's no crime in doing an initial sweep through the source to get any that you need before the main work begins.