Beautiful!
Thanks again Paul, now I can start integrating it into the bigger project.
The only hurdle left is (I think) the high-impedance. From what I've read here and here is to add a 10K pullup to the OE pin, and possibly to the outputs. But the relay module uses optocouplers so that shouldn't be the case.
My assumption is the fast glitching high/low the module does when uploading a sketch, and random state the relays end up in after a reset, are fixed with the pullup.