I hate start FG with plane at rwy. It's innatural and on controlled or busy (like KSFO) airports also disturbing. But for many apts (even controlled ones) there are no other points defined except rwys. One way to solve this problem is definition of parking positions and holding points for that apts (I start doing so using groundnet.xml, these xml files will be contributed, when polished, I promise).
Another way is take alredy known info about rwy and taxiways and calculate nearest holding point position and heading and place aircraft there. IMHO it shouldn't be so difficult to programming and resource consumpting task (but I can be complettely wrong, not beeing so good in C++ and not knowing FG internals well. Pls, don't vaste your time for detailed explanation, "you are wrong, it's very complex task" will be enough. Also I apologize for needless request if this question is alredy resolved in 3.2 version. I'm using 3.0). Programm flow should be: pilot asks for start on rwy XX. groundnet.xml exits? Yes, take nearest holding point. No, calculate nearest holding point. No start directly on rwy allowed.
Another two little, but not so satisfactory user experiences, linked to this question (always 3.0 version). I choose to start on rwy XX (rarely) and I'm welcomed with info 'You are on rwy XX". I choose to start on parking pos YY and I'm welcomed with info "you are on rwy <empty space>" (I'm not on rwy, I'm on parking pos, you fool

And the second one: I move to another airport, using menu Position->Place aircraft on airport, choosing position on rwy and I'm welcomed with 2 line information "You are on rwy XX" and "You are on rwy YY" (oposite direction). I can feel myself as our Lord, omnipresent

Just my 5 cents
Ragards
Pietro
(not yet contributor, dumb tester for now)