I'm sure there are a few that have done it.
I've got the 801A and wish I could plug in an aftermarket head unit. (I can, but then I would lose all the factory controlled things that are integrated into it.)
It would make things a ton easier with my install, since there seems to be some minor glitch in the factory amp that's giving my Rockford Processor problems. Going to the Dealership Friday to see if we can solve the problem with an amp switch.
As far as the packages go, Don't settle on one based on a future upgrade. Look at whats included extra in the 801a and decide based on whether it includes something you really want or not... (heated/cooled seats for me... which is also, ironically, what is preventing me from swapping out the factory Nav! damn MFT... hahaha) There's an outfit (can't remember name offhand) out there making an integration system for the Ford MFT/Sync system to allow these features to be accessed on a Kenwood or other compatible headunit, but last I checked, it didn't support the 2013.
Good Luck!