Do it! You will be in exclusive club. More people are struck by lightening in the USA than complete the great loop each year. More than half those who do, follow your plan. They purchase a ready to go boat that likely just completed the Great Loop and then sell it when they are finished. We wanted more than to just complete the loop
After our loop we will do all the rivers, Lake Superior, the Canadian Maritimes as far as Goose Bay, Bahamas, Caribbean and through the Panama Canal to Alaska.
We wanted more boat that for the loop. We wanted a full ocean capable boat with extensive range. That range allowed us to buy diesel at the commercial docks where fuel was around $3.00 a gallon and you have a pump that pumps at 50 gallons per minute with 300 gallon minimum.
Be sure to take your E bike and a small trailer. They come in real handy to run errands and tour locally.
A few photos of our trip.