If wind is your concern, build it to Florida Code. You list FL as where you live, and their building code is about as good as it gets for strong winds. Build it to survive there and you shouldn't have any problems in Iowa.
Wind is like anything else. Cut a corner and it will fail. Build it right and you will save money in the long run.
As for the quanset hut, it depends on the ratings the manufacturer comes up with for it and how much wind you have there. An engineer stamp is required to have a wind rating. That stamp will tell you what will work and if it's what you want to spend. Most metal buildng companies have this. If you don't like the look of the quanset hut, and I'm one of those who think they are ugly, there are other options.
A leanto is also a wing or a parachute. It woldn't be too dificult to add one to any building, but making sure that it can withstand the wind loads if they are really bad is where you'll have your challenge. For the quanset building, flashing, goof fastners and sealant will make it work.
Eddie