Antje,

You've defined yourself into infeasibility.

The cheap macro lens for 'blad, the 120/5.6, won't focus close enough. Ihr vater is averse to tubes. So much for 'blad.

Mamiya 645 has a focal plane shutter, i.e., too slow max shutter speed with flash. Also its 80 macro won't go to 1:1 on its own mount and your father is averse to tubes. So much for Mamiya 645.

Same goes for Pentax 67.

But and however the Bronica ETR/ETRS/ETRSI has a 105/4.5 that is in leaf shutter and goes to 1:1 on its own mount. Cheap, too, especially in Euros, at www.keh.com Just remember, 645 isn't that much larger than 35 mm.

Good luck, have fun,

Dan