Therein lies the conundrum. If you get a store-bought plane, it all looks flash and, of course, you can’t change anything. If you build yourself, you have to trade off your ability to change things as often as you wish against your desire to make it look as store-bought as possible (for the psychological comfort of intending passengers if nothing else. There’s still plenty of folk whose concept of a home-built is that of a lawnmower engine strapped to a broomstick with some old sheets for wings 😱).
That trade-off is, of course, a personal decision (and one that I have yet to make).