I haven't scrutinized it thoroughly, but this SRFI looks very nice.
Some of the formatting is a little confusing: the prototypes are not
very clearly distinguished from the other text; perhaps it could be
indented differently, and the word `procedure' could precede the
prototype or be right-justifed:

procedure: (car /pair/)
or
(car /pair/)                                      procedure

  Returns the contents of the car field of /pair/.

LIST-REF/UPDATE is sometimes overkill -- perhaps an operation just to
modify the element at a particular index would be worth adding, say
(LIST-MODIFY <list> <index> <procedure>), which would return just the
new list with the element E at <index> replaced by (<procedure> E).

Since random-access lists are (or at least may be, in general)
incompatible with sequential lists, if you have written code to use
SRFI 101, how do you use rest lists in n-ary procedures, and APPLY,
or, more generally, how do you use code that expects sequential lists?
This will be important to address for anyone to actually use
random-access lists.