Actually, individual actions on hold would be doing a lot for the checklist behaviour I described above. I tried to create checklist items by adding sub-tasks that were on hold (in 1.8 SP), and it
almost works, apart from the fact that the group header does not appear in perspectives filtered to only display available items. So: As long as the group header does not fall through the cracks in context view, individual "on holds" would be a great step forward.
My solution for this today is clumsy, but it works: I have one task with a link in the note field to my "On hold" checklist's group header. All items under this group header has an "On hold"-context; "Check list item":
This actually works for the iPhone too, but a more intuitive solution would of course be much appreciated...