This is so not going to happen, but I like thinking about stuff like this.
A single construct, built from blocks, ropes, and mechanisms that serves to interconnect several other devices (levers, bridges, floodgates, etc).
The trick is that a simple scripting language is used to 'program' the controller. Very basic, mostly boolean logic. Simple branching (if/else), no subroutines (or simple assembly jmp style), likely no math at all. The script would define a number of attachment points (or perhaps a single controller would be capped at a reasonable value), and any time anything attached to it changed state due to outside influence, it would run its script. The script could ask for the state (on or off) of any of the attached devices, and force state changes in any of them as well (perhaps incurring a delay to run the script, or even stepping through the instructions at a fixed rate).
The number and type of components required to build the controller would depend on the actual instructions used in programming it. Optionally the controller could require multiple tiles based on this number as well, though whether you specify the size up front and have it cap the complexity, or write the script and are then given a box you have to find room for is kind of a toss-up.
Attaching devices to the controller is done via the normal attach interface, and requires the normal pair of mechanisms, though when you select the controller you also specify which attachment point you want to attach the device to. Optionally, each attachment point could attach multiple devices. The single state seen by the script at each point would be some combination of the states of all attached devices.
For extra credit, the programming term 'bug' came from the idea actual insects would find their way inside the room-sized computers of yore and bridge contacts when they died, causing short circuits or similar problems. Unchecked vermin in the area could pose a problem to a running script, causing inputs to not be read correctly, instructions to be skipped, or outputs to fail.
For extra extra credit, allow setting states on unused connections to implement a limited form of persistent memory internal to the device.