Tenant Rant
It's probably just the tip of the iceberg. - Sounds to me like they're the type that believe "No one can tell us what to do". If you were to tell them they couldn't have pets they'd probably get one and you'd have animal feces all over the carpeting. Sometimes being the nice guy and trying to nudge people into better behaviors can bite you in the butt.
Without being specific on what "REASONABLE" means it sort of left the door open to what they will do. I had nightmarish problems with a renter before. The more reasonable I tried to be - the more they took advantage. They went so far as to change locks so I couldn't access my own property even though I'd never entered without notifying them first. Eventually (after they'd failed to pay rent for 3 months) I tried to evict. They threatened to sue and my attorney told me it would be a crapshoot in the court system whether or not they'd win.
When they did finally leave they stole everything that wasn't bolted down and even some stuff that was.