For us, we have a guy that manages all of these type of contracts. It's kind of like an entrepreneur in the making kind of arrangement, for him. I agree on the hacking issue, which is why we personally don't host Wordpress sites and the person that handles Wordpress size clients makes it very clear that Wordpress provides the platform, security and all, that we provide the design, customization of template, SEO, analytical, etc.

While there are a lot of pain-in-the-rear small clients it is not unique to them nor are all of them pains. We have had a lot of small clients turn into large clients as well, we have had a lot of small clients refer us to large clients. How we personally made it worth while was to find a person that wanted to grow a company, but offered them the advantage of doing it from within a current company. This person is now, managing Wordpress (Drupal and a few others) for several shops like ours. He also receives a commission when one of his clients outgrows him and is ready to move into custom development. It has worked well for us, but it is by no means the bread and butter, but it does save a lot of time by not spending cycles with people that just flat out can't or won't spend the money to pay for custom software.