I disagree with the discussion on leaks. I've had plenty of leaks over a 10+ year of watercooling with no permanent damage ever done.
I second your discussion on Galvanic Corrosion. The issue is that the anti-corrosive fluid needs to be replaced at an interval proportional to your usage of the computer as break down of the anti-corrosive properties is proportional to heat of the system.
The fact that most AIO's are not serviceable is my number one complaint. Evaporation and the need to service your anti-corrosive fluid in a system that doesn't allow servicing is about as dumb as you can get.
Asus Prime Z370, Intel 8700k @5.0Ghz, Nvidia GTX 1080 Ti, 16GB @3400 CL14, Watercooling: x2 MCP355 pumps, x1 280 on front of case, x1 360 on top of case, x1 140 on back of case, x1 240 on bottom of case