Actually this is a feature I’ve been kind of thinking about. There’s no need to split it in two… Only in the CODE and behavior does it need to be split in two. I rarely use approach because of the violent climb and or banking the aircraft sometimes does when I’ve intercepted the localizer and been a dot or two below the glide. What the devs could do is implement an “ARM*” function for approach where the LOC and G/S are “armed” and the LOC could be intercepted prior to the G/S being intercepted without the aircraft climbing. See pics of Airbus PFD/Flight Mode Annunciatior with LOC and G/S armed.
*The “ARM” function could be along with a flight director/flight guidance system that would allow you to arm NAV and or ALT on the ground similar to the Airbus and fly manually via flight director commands for vertical/lateral navigation-see the Boeing/Airbus pics below
Boeing and Airbus “Takeoff Mode” with LNAV and VNAV armed, then LNAV/NAV becoming boxed on the FMA followed by ALT on Airbus and VNAV on Boeing shortly after liftoff.
Some features aren’t mutually exclusive of others and vice versa-maybe I’ll post this thread and others relating to a flight director/guidance system and see what develops.