Focus scale and E-mount lenses?

Have been wondering...how hard or how easy is to employ some kind of electronic Focus scale on the EVF or main LCD? I know that NEX-series uses mainly CDAF, but sometimes I have seen threads about people struggling focusing in low light situations (I.E., landscaping at night) and the suggestions to overcome those issues are always welcome.
Thinking a little bit about this after seeing some thread about birding with NEX-series and how people would like to see a telephoto lens with more reach in E-mount format compared to the 55-210mm... but the CDAF on NEX-series would make that lens a little annoying to use on subjects far away from the shooter moving quite fast from one moment to another and then thought if it was possible that in the future, Sony provides a way to know at what distance the lens is focusing according to the movement of the AF elements on the lens itself and then show it on the LCD or EVF and even control or limit how close or how far the lens focuses(and still use CDAF). I mean, E-mount lenses use a encoded distance scale of the focal lenght on every zoom lens. So how hard it is to encode the AF elements travel and make it work like a digital focus scale and even provide some way to work as AF-D function. Don't know if I explained myself at all. Not my main language, sorry.

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Proud Sony NEX 5 user