I think what we gain from the security of a consistent rule of law, and the protection from the abuse by law enforcement officers, far outweighs the difficulty in having to think through and create reasonable laws. I dont want to trade protection from abuse just because we're to lazy to write correct laws. I don't want the current system of "make everything illegal" + "trust the cops" as the solution for that.
Some type of shoulder, dash cam, or Google-Glass-like device could go a long way towards that. I also think that there can be clear distinction at least when the cops must act and when they cant. Most places seem to have speed limits that are too low causing everyone to drive 5-15 over. But if the chances were high that you would get a ticket for going a few miles per hour over the limit, would you always put yourself in a situation where your are likely to accidentally drive over the limit? I think people would find a natural "buffer" and protect themselves. And speed limits should probably be increased and if the law was consistent and strict, people would find a reasonable speed to travel. Most of the time driving the actual speed limit becomes dangerous when everyone else is going that much faster. Or, specifically regarding speeding, cops could be prevented from pulling someone over unless they were traveling at 15mph or higher over the limit. I don't think it's hard to work out the details.
As for smokers...walking past smokers is a minor nuisance, people should just get over that (IMHO). I recently quit, switching to e-cigs, and people still cough when I walk by. They think I am smoking because my e-cig looks like a cigarette. It is all in their heads (there is no second hand smoke with e-cigs). Second hand smoke only becomes a problem indoors. And any rude smokers should be asked to make way nicely. (I used to always try to keep away from doors to buildings and especially keep my distance from children). But I'm not sure a law is needed here. Smoking is largely on the way out in the US.
As for pot, I think that should be legalized.
As for parking, that is not done by cops usually. And I can't remember a time when parking was ignored as a minor offense. Most towns see those tickets as cash cows.
While I appreciate what you saying, I dont think that is a good enough reason. If the law was applied consistently, people would adjust. Right now people just roll the dice against how much they can get away with. And cops walk around with power they should never have been granted.