[plt-scheme] Should PLT Scheme have two R6RS namespaces?

Right now PLT Scheme provides the SRFIs in a immutable-list compatible
form. Correct?

This works well for using #lang scheme. It is ideal for that.

There is also a want for using pure R6RS implementation of the SRFIs
when using the #!r6rs language.

R6RS code should not use the immutable version of the SRFIs; it would
be a hassle converting between immutable and mutable lists.

Could we have a convention for, when using the SRFIs, that the
PLT'ized version have a regular number and R6RS specific versions have
the colon-prefixed number?

The next step would be getting the R6RS version into PLT but I am not
sure how to do that yet.