540lbs useful load. Are the people clothed at 240lbs each or naked, that is are they 240lbs each sitting in plane? My Aeronca Champ 65hp weighed about 650lbs empty and about 1250 gross, 65hp Cubs are very similar and both have similar speed which is around the speed you want. You want an old Tailercraft or Cub or Champ. All three had some model deignation of side by side seating. You just want it "modern" that is lighter, easier to maintain and easier to own.
Maybe you can compromise up a little? Have you given any thought to motor glider? I do not know the regulations in Switzerland but it may behoove you to find out more about motor glider rules. You wouldn't hardly tell the difference between a cub like plane or a high wing primary glider except the registration. And the rules to become a licensed glider pilot may suit you as well. "I think" max weight to get glider instruction is around 240lbs at least it isn't unheard of.