What I was thinking about this topic, is not introduce another datum
like :keyword
or #:keyword but instead create some argument parser procedure like used
for command line arguments. This is backward compatible and build upon existing
knowledge.
There are several such parsers; they are independent of whether keywords are self-quoting or just plain symbols. I just sent out the description of (chibi optional), which is meant to work with ordinary symbols that you have to quote. Standardizing such a library is probably a Good Thing; whether we should standardize self-quoting symbols, and in what shape, is the issue right now.