Patched the worrying bit with a bit cut off an old aluminium door bolt. It's stuck on with superglue and bicarbonate of soda - don't think it's going anywhere, solidly stuck on. I'll give give it and the other bits eroded a touch of black paint. The small overlapping superglue and baking soda section joining the motor to the controller at hat point, can be broken off and filed down when I need to replace the controller, or dissolved with acetone if necessary (could also dissolve the motor's paint).
A drop of superglue went into the bolt hole, but I unscrewed and unseized it before the superglue set.
I look forward to seeing how long it takes for this hat to be eroded away.
If this does fall off, I'll secure it with the stronger (and more heat conductive) superglue + graphite potion next time.