It doesn't sound like this should be an extension of acs_events at all but it might be worthwhile investigating the use of the abstractions acs-events provides. I used acs-events when I ported over the old Events Management package and found it straightforward and easy to use (of course, it appears as if it was essentially abstraction of the old events package so it fit with the updated events package very well). We were going to work on calendar integration but haven't gotten that far (yet). Anyhow, I just wanted to point out that acs-events *has* been used.
