I used to have a similar rule as OP, in that characters had to be non-evil, and while not necessarily heroic, at least had the capability to do heroic things.
I tried to expand that in my most recent campaigns though (they were intended to be short, so a good trial of how my players might handle such things), and just had the rules that characters couldn't be disruptive for the sake of being disruptive, and they had to have a reason for adventuring (I've no interest in running Bakers the RPG for station squatters as another recent thread coined). It worked pretty good.
That's pretty much how I plan to run games now.
I tried to expand that in my most recent campaigns though (they were intended to be short, so a good trial of how my players might handle such things), and just had the rules that characters couldn't be disruptive for the sake of being disruptive, and they had to have a reason for adventuring (I've no interest in running Bakers the RPG for station squatters as another recent thread coined). It worked pretty good.
That's pretty much how I plan to run games now.