Patrick,
are you sure you aren't creating a theoretical mountain out of a practical molehill? I've been using OF for a couple of years, with lots of actions in on hold contexts, and while I believe I understand your complaint, it just hasn't been an issue in my practice. Perhaps the difference is simply in how we use the tools.
I have a handful of on hold contexts:
Looking for
Waiting for
--Calls
--Email
--Mail
--<people>
A perspective that shows those contexts, grouped by due date and sorted by due date, showing remaining items
I typically work out of context mode, viewing available actions, grouped by start or due. I don't see those on hold items at all there, but they'll block progress beyond them in their project, of course. When I do see them is when viewing things in project mode (with remaining actions), typically when doing a review or focusing on a single project, or in my daily start-up process, which includes taking a look at the "Waiting and Looking" perspective mentioned above to get a reminder of anything I should be watching for. If I see that there is something I'm waiting for that is now overdue, I double-click on the action and get a new window focused on that project so I can see the whole picture and decide what needs to be done. I will see the overdue item even if the containing project hasn't gotten to it yet, yes, but I still most likely want to take some corrective action (example: I'm building a new disk farm, and I haven't finished designing the filesystem, but UPS hasn't delivered a drive when they said they would -- I'm going to want to find out why even if I'm not ready to use the drive!) I do assign a due date to most everything that is in one of the on hold contexts, and usually have the "no due date" group closed. I think that keeps items out of my active sight until there is need for attention while still allowing me to easily check up on them.
I was interrupted while writing this and Brian has contributed his piece in the interim. I notice that he has a completely different read on the situation (and that mine differs from Lucas' as well) and hope that between the three of us, we've at least straddled the target :-)