> so such motors require frequent maintenance for changing the brushes.
Define frequent. I maintain machinery with brushes so I have a decent idea of what life span should be depending on the environment. If the housing for the slip ring setup is well protected from dirt and the slip rings aren't cleaned by a cave man you can get a few years of life from the brushes.
If the desired location for this is a car, then a few years of life that requires half disassembly of a motor isn’t going to work.
That does not sound worse than replacing the spark plugs in a Subaru engine.
The slip rings are not in the middle of the motor, they're on the butt. I know car makers don't always try to make things serviceable, but it'll be hard to make it hard to replace. Probably the only issue will be needing to remove other parts first to get to it, if anything.