Can the dash from a 2015-2017 Cascadia fit the 2008-2014 model

Oofta...so much learning needs to take place.

First of all...your "four-way flahser" is indeed your MSF. Aka Modular Switch Field. This can be moved wherever as long as your daisy-chain stays in tact as well as any of the associated smart switches.

Next to address your manual fan. Now depending on your setup, you have an air activated fan. I would have to look up your specific unit, but I'm guessing it's a Horton air clutch. The 5-10 seconds to "disengage" the fan is COMPLETELY normal. There is a debounce time for a switch to toggle as well as the air to completely exhaust from the hub.

You just said you plugged in a new fan switch. So then it would make sense that the MSF would complain about an extra smart switch that you did not parameterize correctly for.