Remove the players from the radar.
Have a high and low profile system. Low profile means that you're just minding your own business and are not on the radar (unless a player calls Lester and reveals your location). High profile means that you are shooting and killed a player or have a wanted level and you pop up on the radar of nearby players. The reason why we need a bad sport system is because Rockstar put all of us in a radar and made us accessible to every player. Free Roam should be just that, Free Roam, not a death match. If a player wants to kill other players then he should be in a deatch match mode, NOT in Free Roam. Free Roam should be a pleasant experience, with us showing off our progress and cool new toys, not a deatch match hell where you get gunned down by assholes who wait outside of your apartment.
High Profile - On radar to nearby players. The distance depends on your wanted level ( a range matching GTA4)
Low Profile - On radar only to players who used the Reveal Players perk.
If Rockstar removed or at least limited the visibility of players on the radar, GTAO would be way better.
I agree with the map thing 100% and think it is a good idea, however free roam is not to show off your toys and GTA is not a "pleasant" experience, it is not the Sims. It is to be enjoyed, yes, but free roam would be nice if had the map you described and I think that alone would alleviate 95% of the random killings at least, since people cant track you unless your causing trouble yourself. I would never use it but I think R* would benefit for a "peaceful free roam" mode for the casual gamer. Again though, the map idea is very good, I would love to see that implemented as long as you can still see your crew on the map at all times.