IMO, No rest day. We have 358 other days of the year to rest.
No optional out and back loop on a “rest day” for that matter.
Mandatory Century Day.
If needed make the day after the century a short day like we did in 2014.
End in the NE corner of Iowa.
I do like the idea of Friday night on the Mississippi river then travel to the end town up or down river.

In the end, I’ll ride wherever the RAGBRAI arrows point to.