Right; you've got to ask yourself here - what approach are you flying? Of course a VOR/DME approach with minima/OCA(H) based on tracking a certain VOR radial to a certain DME. While LNAV/VNAV are pretty accurate navigation systems it doesn't say on the chart that the VOR radial is to be superceded by your FMC data. While GPS approaches are indeed published and GPS is indeed extremely accurate, the method by which it gets its data can be removed at any time, or blocked by anyone (as happens quite often in the UK.) Don't get me wrong - I think GPS is great! Much better accuracy than my IRSs!
So then, what happens the next time someone hits a mast or a hill or what have you as a result of map shift etc (I know not too likely) and the FDR shows LNAV/VNAV engaged? What approach were they flying?
I reckon fly your VOR/DME approach in VOR/LOC /equiv. plus V/S to MDA in your altitude window. Modifying V/S then allows you to compensate for height restrictions. By all means check LNAV etc if you wish.
Or you could always hand fly it with raw data - much more fun!!!