Lowest possible is... 1 subsidized account per 10,000 blocks. Which is - ~3 subsidized accounts per day?

I would have no qualms about this either, if no one else from the community (developers mostly) was intending to take advantage of the subsidy pool. If it was going to be Steemit Inc, Blocktrades and Anonsteem dominating account registrations as usual, it'd be best to make them burn for it. However, if a developer comes up with an impressive plan to market their apps, I'd like to see them get access to at least some subsidized accounts.

But yes, that seems far fetched at this stage, because we haven't seen a single developer on Steem with any marketing plan whatsoever in the past 2.5 years.