I don't mean to be negative, but just a word of caution: personally, I think you're heading in a direction that's not well-supported by the tools and will ultimately yield disappointing results.
I think this
post by Brian on a slightly related topic highlights the issues nicely. He suggests that items stored in your calendar app and items stored in OmniFocus are really two distinct types of data.
And, of course, if you're following a GTD approach, be sure to read
David Allen's book (if you haven't already). He has some very interesting things to say on the different roles of calendars and action lists (like OmniFocus).
I hope this is of some help, even if it's not what you were hoping to hear. :-) Perhaps others might have something to offer that's more supportive of your original plan.
-Dennis