There is a really simple motto to follow with all things German -
Cars
Motorcycles
Women
Guns
Etc.
Don’t fuck with anything under the hood. Maybe - MAYBE basic maintenance.
What you’re paying for when you opt German is the over-engineered, über precision, that comes with Teutonic obsession to detail. The whole idea behind German engineering is precisely to have thought of everything so you don’t have to.
Americans are sort of cavalier in this regard. We typically view customization as a need, not a luxury. And thus, because we view things this way, we typically want things built in an accessible way.
The thing about the VP9 is, aside from the striker dropping, the only thing it might need besides springs and oil is sights to your preferences.