Hi,
in my experience, READ-FILE-INTO-{STRING,BYTE-VECTOR} are very handy. However, maybe half of the time I already receive an open stream and need something like R-F-I-{S,B-V} but for streams.
I already submitted the attached patch in mid 2012. Nikodemus didn't want to introduce new functions at that time. Please consider it again.
The patch adds the functions COPY-STREAM-CONTENT-INTO-{STRING,BYTE-VECTOR} which implement this feature. Despite the new toplevel functions, little new code is introduced since R-F-I-{S,B-V} can be implemented in terms of the new functions.
Thanks in advance and kind regards, Jan