After couple of years and many ideas, I have finally settled on a design for my experimenter's board.
Say hello to EduKit BoosterPack.
The EduKit BP comes with 1.8" color LCD and 8 accessory connectors. Each connector provides access to power and 2 or 4 MCU pins and are used to connect accessory boards. Those boards will allow user to perform tests and experiments, and could be used to teach about MCU's. There are also 4 jumpers on the board, which are used to change LCD's connections. LCD can use SPI1 (UCA0) or SPI2 (UCB0,) CS and D/C have also 2 possible connection options.
Accessory boards can be simple, for example switch, LED, or potentiometer, or can be more complex, like shift register, mic with amp, sensors, MIDI, GPS.
The EduKit is meant to be used with MSP430G2 LaunchPad (though it could be used with any other LP,) and will come with a library that will allow easy setup and use of LCD. User can write his code and then display results using one of the included functions (text, bar graph, etc.)