What syntax support should appear in SRFI 231, the followup to SRFI 179?

I don't think much about syntax, so I'm not the right person to lead on
this issue.

Jens Axel Jens Axel Søgaard recommended SRFI 42-type comprehensions.  We
haven't yet determined why SRFI 42's example programs don't run on
Gambit, but perhaps it would be good to discuss before then how such
comprehensions would look in use.

What other syntax support should be included in this SRFI?

Brad