The rule-based sending feature, coming in the next release, will allow you to send based on search results as you wish. I plan on having the same powerful rulesets available for the export process, so this could be used to determine how many of a certain type of user there are - at least until I have rulesets implemented for user listings.
A number of subscribers message code, with fudge factor, is quite simple. I will definitely be able to implement this for the next release.