Got it, just wanted to be clear we'd been poking the same turd. Things getting lost in the translation, even my #12 should say O.M's.T = (a)+(b) more clearly than I actually typed it.
But now it is clear:
(i) use selected vertical modes only;
(ii) use DES but shadow the vertical limits with FCU due to anxiety and OCD issues;
(iii) use DES the way the designers and engineers intended to.
One of the tiny reasons I may subscribe for (ii) on many days is that when a step-down constraint is satisfied the ALT CSTR does not display on PFD. What's the US version of A thousand mosquitos drained the camel, death by a thousand cuts?
Never mind, moving along. How do you (well familiarized) guys feel about using managed speed for deceleration and flap extension - if the ATC scenario allowed it?