Update after some sea-trail:
It turned out to not work as I intended it to. Working well at the dock when tested, it does not work in big swell offshore. Reason being that the AP Linear Drive motor power is "open". So the swell turned the wheel fairly easily. The remedy to that would be to add a relay and short the motor whilst the brake is engaged. But that is a big change and could have other unwanted consequences, so we've opted to remove the function. Great in theory, but not in practice. Live and learn :-)
Decided to keep the blog-post anyhow, since even failures can teach you something.