Yes, but you get more different characters with fewer keys In my case is absolutely the best way as I need different dead keys while typing in different languages... and the modifiers stay the same...

Regarding the fourth level: I've discovered that the default "FOUR LEVEL ALPHABETIC" scheme reaches the fourth level via shift or caps lock: you basically have two levels + two capitalized versions of the very same letters. But we could change it to a plain "FOUR LEVEL" scheme: this way you should reach the fourth level via shift + Fn.