about witnesses.. often they will say something like "im calling the cops" and they will pick up their phones and call... you can take them out before they make the call and avoid a star that way... as for stealth, it is certainly not working properly, it feels broken and more or less useless... you have this big detailed world to roam in, and so many places that invites to some nice stealthy action.. but then yiu attempt to be stealtjhy and you magically get stars more often than what is reasonable when having access to suppressors and 'stealth mode'
the thing is, with some changes that makes the stealth work, along with perhaps some good places and reasons to put it to use in the game world.. like, perhaps you can place a safe in certain locations.. say some warehouse down at the docks, make it restricted at night and have some guards walk around.. you'll havge to sneak around to get to the safe.. you can do it undetected, or you can take the guards out.. taking out guards without being seen helps you avoid a star.. if you are seen, you will get a star unless you are quick enough to take out whoever will set of an alarm.. and then you may have to be fast and rudn and hide somewhere...
this would work if just the stealth parts were fixed.. the way the AI works when cops searches for you is alright as it is, as you can hide close by as long as they dont see you.. i have had some pretty fun cat and mouse play this way, jumping over fences, up some ladder, and so on.. you can see the direction they look at on your radar, and so it is fairly easy to avoid then if there are bulidings around
but as it is now, it truly seem like hit and miss and you end up having to escape the cops because they magically knew you committed a crime.. its usually easy to escape because it takes some time for them to arrive, and you can find a good hiding spot near by in the meantime... but it completely kills the immersion when wanting to be stealthy.. making it seem pointless and as if only for show.
and you got a set up that could rival games that are purely based on stealth.. because the level of detail, and and places to hide or sneak around is just awesome.. it would offer a massive amount of fun