I don't disagree with your concerns, but the way I see it we should either go all the way and ban stuff like alcohol, or accept that if it's legal, then legalizing marijuana if anything will improve things as they are.
I think alcohol by far the more dangerous drug, at least based on what we know now, and yet it's completely accepted in society and often there's even pressure to 'partake'. I would not argue that weed should reach a similar status, and honestly based on the effects it's unlikely to, but even if it did, it would be an improvement.
Plus, when you consider the typical 'abuser', it tends to be an either/or situation when it comes to weed and alcohol. I knew many more people who exclusively use one or the other as a coping mechanism than people who use both.
My ideal approach to figure out what the longer-term impact of weed could be on society is pretty much exactly the coffeeshop approach: don't make the substance as easily available as alcohol (or cigarettes, in many places), but make it relatively possible to get legally if you want it. Basically, give it the status of something like a massage or going bowling (that might be a pun there, I'm not sure). Not something for every day (I'd hope!), but still something easily accessible and defanged of its status as 'illicit'.