sorry,. my text should have said VNAV, not LNAV, of course we are constructing an artificial Vertical not lateral profile!
One thought though. With the advent of GPS, will we see the elimination of the need for ILS for suitably equiped transport category a/c?
After all a GPS-autopilot coupled approach could substitute for the ILS (and we could use the triple-INS and DME/DME as backups/additional voters).
It would also allow (along the lines of MLS) curved approaches.