Haha Wow, You pretty much described one of my current builds to a tee. I used a black Micargi Jetta and black 66cc kit. I'm using a big sprung gel cruiser seat instead of a banana seat and I'm using the stock chrome Jetta handlebars on a new black triple tree and stem. It has a chrome crank and sprocket. I'm using the bigger peanut tank with some chrome car door trim around the rim where the top and bottom half of the tank goes together. It spruces up the tank a little and goes with the other chrome bits. The motor is a tight fit and not the easiest build but very rewarding when you get the final product.
You're gonna need either a short intake or an offset intake. I'm using the RT carb with a short billet intake and its a tight fit. I can only use the stock air filter because the aftermarket one is just a little too big and I cant find anything that would fit. I needed to use an NT carb top cable inlet instead of the longer one that comes on the RT because of space and to use my standard throttle cable.
My bike is pretty much all together but I'm still waiting on my custom sprocket from kings. I live in a really flat area. So I went with a 26 tooth. Using the gear ratio calculator I found that the difference between common ratios of the 26" tire and the 20" tire to be about 10 teeth. In other words to get a close ratio similar to the stock 44t on a 26" tire, you would need to use a 34t on the 20 inch wheel. So, your idea of going with a 32t is right on.
I'm a short, light guy and the 20" fits sooo nice. The seat is nice and low. More like an actual moped. Instead of being way too tall and awkward feeling for my size, like my first Mab was. It was a 26" beach cruiser and even with a low laid back seat post(as well as a shortened frame seat post tube) I still couldn't get both feet flat comfortably while on the seat.
One thing I think you should add is a tail/brake light with turn signals. It makes a huge difference when you do. Makes people able to see you and know what you are doing better. It especially helps when turning left while someone is behind you. They will see what you plan on doing and not try to pass you just as you go for the turn. I use these cheap setups I found on amazon.
http://www.amazon.com/Bicycle-Bike-...sim_sg_31?ie=UTF8&refRID=08GGM1PNKNQPV7JTB6H0
It gets the job done for a lot cheaper than putting something together from separate components. The controller/switch isn't the greatest looking thing but does the job pretty good. The only bad thing other than being made out of cheap plastic and the looks of the controller is that while you have a signal on the horn also will play until you switch it off. Its quite annoying to me but a quick snip of the speaker wire took care of that. I never used the horn on it anyways because its not loud enough to be herd by anyone other than you and anyone a few feet away. It has lights that come on, on the controller to let you know the brake light or turn signal is on.
I guess great minds think alike haha. You've got some good ideas going. Can't wait to see some pics.