Speaking with my editor's hat off, I wonder whether we're too worried about compatibility.  While there is some code that depends on SLIB and SRFI 60, let's hope that there's even more future code that depends on SRFI 151.

I'm reminded of the story from the author of Make that I've heard repeated: When asked why he chose to make the difference between space and tab significant in Make files, he responded that once he realized that it was a mistake, he already had ten users, and he didn't want to break their code.