Personally I'd like for you to make an upgraded CSE before you go to the 83+. Would making a calculator with a color screen be easier with your current PCB?
So, making another model work would require starting completely from scratch. While I don't mind making another one, once this one proves to work, I don't have the time to do two in parallel.
Also I would have to buy a couple of CSEs to get going.
About color screens, I found them to be a real PITA in many aspects. There is the higher data rate, bad driver support, high power draw, evil hotbar or tiny pitch FFC connectors, price (to some extend). If I do another one, I promise it will have a color screen though
For the time being, this calculator will have a composite color video output. You can even hook it up to a small car monitor or a TV:https://www.ebay.de/itm/4-3-LCD-TFT-Car-Auto-KFZ-Monitor-Farb-Monitor-Display-fur-Ruckfahrkamera-DVD-FN/252731070687?hash=item3ad7f218df:g:MpMAAOSwOgdYzKDZ