This sounds like a fun project! Follow your dreams!
You might be able to make a hardtop with canvas sides as Randy suggested. Think about having it fit tightly to your side rails when down. I like the idea of using the telescopic lifts from an old pop-up camper.
I had worked on this concept for a long time while designing my boat. Never quite came up with the perfect solution. I even designed a set of lifts that would have been driven via an electric winch & pulleys.
Keep us informed of your ideas.
GOOD LUCK!
Dan & Denise, Preston CT
2009 22 1/2' Hand-Crafted Tri-Hull Wooden Pontoon
"All Spruced Up"
1985 90 HP Evinrude 2-Stroke
2008 Chevy Silverado LTZ Crew Cab
2005 Boat Wheels Aluminum Trailer