Speaking from current personal experience, I believe a number of experimenters could benefit from availability of a generic bi-directional level-shifter board - preferably one that connects to the 40-way expansion port (avoiding patch wires by taking VBus to one or more jumper-configurable and/or variable regulators). The board would also present light regulated rails for attached circuits.
One distinct advantage of using the 40-way expansion would be to safely enable/disable the configurable regulator(s) and logic by merely sniffing the switched PIC supply, eliminating potential noise transfers to the PIC supply, and would simply offer the 5x'D' connections (as per the EB006) with level-shifted outputs.
The availability of all ports would also permit some to be configured as open-drain (such as for I2C), and others push-pull driven for higher-speed logic.
Just a thought
Best wishes for a happy and prosperous new year.
Brendan.