Jerry,
The existing horse (today's mBIT-X) you left the gate on has lots of inertia due to the numbers out there. If we need more I/O, features, I would be inclined to make it where it's readily upgradeable for existing users. In my thinking that would mean leave the main board "essentially" the same (except for fixes) and focus on a pluggable Raduino-II which uses an inexpensive STM32F103BT6 at <$3 (the 8T6 has 64KB, the BT6 has 128KB flash....easy to mix them up) and add optional interfaces. That way the upgrade expense is held to a minimum.....yes the Si5351 stays on the Raduino-II and that makes the Raduino-II very portable to other products.?
Many of the color LCDs out there are around $10 and have SPI, IIC, etc interfaces so you don't have to go with a parallel interface.
By the way, there are some small differences between the STM32F1038T6 board they call a "Blue Pill" and the "Black Pill" but they are flooding the market as China blows out the manufacturing pipeline.
73 Kees K5BCQ
