That is a good idea. I ordered another printer for disassembly, awaiting delivery any day now. The reverse engineering then goes in a few steps:
First I need to get to the contact on the pcb, because adding hair wire to the print head, though possible, is tedious. After soldering tap wires to all contacts, I will verify voltages with a scope. This is needed to avoid damaging the logic analyzer in the next step. https://www.saleae.com has a great collection of those, and I am happy to have received one of the first of the new generation. Connecting those to the pins should make the protocol immediatly visible.
I also assume that we have multiple shift registers in parallel (clock, data, set), but there will likely be additional pins for firing, head temperature, and maybe other diagnostics. Plus GND, logic power, and nozzle power.
We will see.