If you want to make something onto your A-pillar you'll have to make it in a way that the A-pillar trim can still fold away when the airbag deploys.
There's a reak-away clip in the middle that allows the trim to get away from the A-pillar without flying through the car (into your face),
so you'd have to construct everything onto the trim, without screwing into the actual metal of the A-pillar.
And you'd have to make sure you don't come too close to the windshield too, as doing so might make it impossible for the trim to separate properly.
As for your search: seat is "stoel" in Dutch, so maybe you can search for a topic and read it with Google Translate?
Unfortunately for you Wouter is wrong in saying that there's a topic on this. There ARE however several people who've replaced their seats,
so you might get inspiration from those. A couple from the top of my head: Franzz, ****, wvz, EJS and Mechanx. Do a search in the showrooms...