Ok.
First: Limit of characters. I'd say 2-3. No one is really going to need more than that in this game since one character is a lot of work. Also make them non-deletable, unless asked for, which would reveal thievery.
Second: Outlines of things behind buildings. This is the biggest becuase a thief can just hide there and no one can stop them.
Third:If someone commits a crime, and you follow it, you should be excempt from commiting a crime against them. Most likely only freedom from assult and murder. Maybe allow theft if your following a theft clue to retrieve an item.