As of right now, I think the only elected officials in the Midwest are Brewer and Dereich, two members of the Alþing. Does anyone have any evidence to the contrary? That means that all officials in the Dude, Where's My Government Officer Amendment and the Holding Our Senators Accountable Amendment who are empowered to appoint temporary stand-ins for any of those positions are vacant.
As such, I believe the way forward is for Brewer and Dereich to choose one of them to become PPT. This PPT will then immediately take over all of the responsibilities of the Governor and the Archduke, which will include the appointment of a temporary member of the Althing and temporary Regional Senator, and the administration within 10 days (presumably something like July 31-August 2) of a special election for Governor, Archduke, one of the Althing members, and Regional Senator.
It's Dereich, Gass, and RFayette in the Alþing.