For a lot of the small schools scheduling totally depends on your talent level. If you have a very strong team, you want to go out and play larger schools that not only help you in the rankings, but gets you prepared for the districts and state tournament. Now smaller schools that are not very good, are going to play a minimum of games, do not have a lot of kids out typically and are not going to be out looking for the best competition because they realize they are not going to win districts.There's always going to be a tradeoff between travel and playing more schools across classes. For football the districts are fine like you say. Once a week, but there also are kids at smaller schools traveling for multiple levels throughout the week. But still, football it's mostly fine.
For the other sports it would be tough. I'd say maybe a district system based on geography and class, but maybe for sports other than football or ones that have a lot of games allow the districts to include schools from two classes.
Baseball is crazy. Ames last week had 7 games and will have 7 games again next week. Very fortunate to be located in central Iowa. They have 12 games against CIML teams plus play Indianola and Cedar Falls, plus have been fortunate to get some of the better 3As like North Polk, Ballard, Boone, etc on the schedule in the past.
Sioux City schools, Council Bluffs, Mason City and Ft. Dodge play a lot of smaller schools and also travel a lot more. I'm sure a lot of the small schools are in travel hell for baseball and softball. It also looks like a lot of schools simply don't play a full schedule while the 4As, at least in Central Iowa max out at 40 games or close to it.
Schools like Cardinal in softball during the 90's when they were winning state championship were playing large 4A schools like Burlington and IC schools, while teams closer to them like Ottumwa refused to play them, so they were forced to travel.