> In this case both fonts-gust-{texgyre,lmodern} and
> fonts-{texgyre,lmodern} seem acceptable, so adding "gust" should be
> done only if "needed" by the above vague rule.
In this case I would not add the gust and stay with fonts-texgyre.
Now, if someone can propose a patch based on the current git of tex-gyre and lmodern ;-))) otherwise I'll work on that in due (more or less) time.
Norbert