What about considering making the end town an 8th overnight town? It would need to be big enough for camping in addition to all the cars parked around town. I think the pluses for some people would be:
1) The chance to celebrate completing RAGBRAI in town.
2) It would be an economic boost to the town.
3) Teams that have busses going back home wouldn’t face tough late night drives home.
4) Longer last day mileage would no longer be an issue
Also a smaller list of larger end-towns to rotate between would encourage towns to have an ongoing RAGBRAI committee and not have to start from scratch each year.