Hello,
Here are my personal impressions on this topic:
Official FIDE time control are 3+2 for blitz and 15+10 for rapid. I would suggest to change the “5-minute” and “15-minute” cadence respectively, hoping 5-minute and 15-minute folks won’t get too upset by this major change…But to adapt ICC pools to the Official FIDE time controls seems to me the best option.
The actual “3-minute” pool has many hardcore aficionados… But I myself have noticed this pool has quite cannibilized the normal “Blitz” rating category(I mean by launching seeks on the server), which is quite an annoying fact too.
But well, maybe people now are too used to this pool, so… give the dog a bone 