I took a look at the subscription system -- the PHP looks too useless to bother making a mod in there. But, I was thinking that maybe I could adapt some code out of it and copy it into my hack. (Less file edits because the functions would be in a new file instead of hacking into an old one.)
I'll also be adding some code that adds events from vbEvents into the calendar pages too, so the events will show up there.

That shouldn't be too hard. A couple quick mods to calendar.php should make that work.
I have a quick question though -- Who here would like for this hack to be HTL-compatible? I've already figured that HTL is the easiest way for me to export this hack, but from there I could generate an installer... I'd like to see some votes on the HTL.