Only you can answer the question of your sanity.
My two-group commercial's boiler is only half that size, 5 litres, and 3300 watts. To run it from an ordinary power point I removed one of the jumpers from the elements so it's now 2200 watts.
Plenty powerful enough in the steam department still and quick recovery. The only time it seriously loses steam pressure is if I draw lots of water from its tap. Never from steaming milk or brewing or both.
That would of course also happen with the full 3300 watts, but recovery would be quicker-not that it's slow now.
I'd expect that with 11 litres, your main consideration if you disable some elements is the extra time for initial heating up. There should still be sufficient heat and steam once you steam lots of milk and brew lots of coffees.
What about the weight? Can your benches take it?