Note that the OTS infrastructure works better if there are fewer calendars, not more (to a point at least). The issue is that OTS clients create incomplete proofs by default, to avoid waiting for a confirmation. So to verify a proof, the calendar data needs to be available. More calenders means more data for the whole community to backup, and more chances something gets lost.

If someone, eg, wanted timestamps once a block it would be much better if they just paid me to do timestamps once a block than setting up their own calendar. Which incidentally is exactly what was done for the Guatemalan election project: the company doing it paid me a few hundred dollars to pay for fees of doing almost constant timestamps.