hop you liked the presentation and devoxx :)
For manipulating the revisions of an entity, you must just remember that the id of an audited entity consists of the original id and the revision number - which is normally an increasing sequence. (The revision number in fact is a relation to the corresponding revision entity).
So, for tagging, or "keeping track of when things were published", I guess an entity which would remember the (original) id and the revision number of the entities tagged would suffice.
For removing old history, an ordinary bulk delete of all entities with revision number smaller than the currently exported one should work.
Let me know if you run into any trouble.