Maybe I would favor using x^{2}y in textual context too, since there is no good solution, and it is simpler to implement and explain ...
Ok by me. Doing the simple way (always add braces) first seems reasonable; if it turns out that the feature gets used enough and people really don't like it, the output can always be tweaked later. I can add these to texinfo.tex and texinfo.texi, etc., easily enough. Do you have time to add it to makeinfo? Thanks, Karl