Isn't it just a #6?
Dosn't the housing and nib just unscrew out of the section?
I ask because I am ordering that as my next FP but I was going to order a B nib from Meisternibs. If it is anything like the other FP's that I have made it should be very easy. Meisternibs.com even has a few videos showing how.
Yes the Majestic's nib is replaceable with a #6 nib either for sure with a Bock or a Heritance or (to be confirmed) with a #6 Meisternibs one.
As written above, to dismantle the nib just unscrew the housing (holder)-feeder-nib from the section and then pull the nib and feeder out of the holder.