There are guys that use pontoon boats in the Caribbean.
Here are my suggestions...
1) Start with a 25 or 28 foot pontoon. It will give you more stability.
2) Definitely select the ESP package. The twin ellipticals and the traditional 3-log boats will give you more speed and just as much stability on a lake, but for your application you would want an ESP setup which behaves like a mono-hull.
3) Big engine. 250hp or better outboard and frankly, I would seriously consider an I/O for the added stability the weight would give you.
4) Get the extra gas tank option and the in floor storage.
5) Bennington has some options/packages for any boat that will be in contact with sea water. Buy 'em.
6) Equip your boat with real emergency and safety equipment EXACTLY as if you were going out on the open ocean. That means a real marine radio and in my opinion, a GPS and a fish finder, which can also find the bottom for you the EASY way. I haven't sailed the Chesapeake, but I have heard that you have to really pay attention to the tides and that sand-bars can be an issue.
7) Life jackets and all the proper safety equipment, including a flare gun, are MANDATORY.
Now don't get me wrong...
If you pay sensible attention to the weather and tides, you shouldn't EVER have any problems.
But if things go wrong, they can go wrong in a big way. You want to be able to run away from it (bad weather for instance) and you want to be ready if things really go sideways.
Where I boat the SOP for when you find yourself overboard is to stand up.
Where you're going, you need to take safety seriously.
Other than that, I think it's a FANTASTIC idea, and you'll make more than a few other boaters jealous.