Would it be a farcial idea to write a new keyword SRFI that unifies all
the existing keyword standards? It would keep the three old syntaxes,
but disallow forms of them that step on each other. It would not
introduce any new keyword syntax. #! reader directives could be used to
turn the three syntaxes on and off in any combination; implementations
could pick which ones are on in the default syntax so their current
behavior doesn't need to change. Procedures to work with keywords could
be copied from SRFI 88 and/or elsewhere, or left unspecified.
Speaking with my editor's hat on, this is something that should have to have a real implementation rather than be speculative. Seeing how the different systems interact in practice would be important. Would you be willing to do that work?
Speaking with my editor's hat off, I don't like the idea of the inevitable complexity that would result. I'd rather see implementors discuss their experiences with different approaches to keywords, then pick one and implement it uniformly rather than try to implement compatibility with them all. Any particular implementation could be backward-compatible with its old version of keywords, but implementations in general would move toward a single standard. Of course, it may be hard to get any particular implementer to agree to do this, especially once he or she has already implemented another approach.