I've been thinking of going with the "one action point per encounter" rule myself, except that doing so removes APs as incentive to keep going after you've started to burn through dailies. There's no reason to push ahead for one more milestone if both APs and item daily powers are no longer limited by said milestones.
What I'm thinking of doing is saying that you get one AP/encounter plus one per milestone. IOW, after your first milestone of the day, you now have two per encounter. If you reach two full milestones, you have three APs, and so forth. That's going to make characters really nasty in late encounters in an encounter-heavy day, but I think (as long as the DM plans accordingly) it could be made to work, and make for some really interesting combats.
Of course, if players have more APs to throw around (even one/encounter is an increase, let alone what I'm talking about in later encounters), it means elite and solo monters need to have more, as well...