Mike, I understand what you say about VNAV, but (correct me If I'm wrong) the mode control panel will always have the cleared level, set in it. the FMC will (i believe) never have a stop altitude in it that is more stringent (lower in a climb, or higher in a descent) than the ATC cleared level.
The FMC may well have some descent and climb criteria (ie below a level by a certain point during descent and vice versa), but surely noone is going to rely on the FMC and VNAV to make sure they stop at the cleared level - that should always be in the MCP.