I don't have an answer, but I am having a similar (same?) issue. When you get the "Modern Setup Host has stopped working", go into computer management and take a look at the most recent application error. Mine always looks something like:
Faulting application name: SetupHost.exe, version: 10.0.10240.16384, time stamp: 0x559f385f
Faulting module name: msvcrt.dll, version: 7.0.9600.17415, time stamp: 0x545055fe
Exception code: 0xc0000005
Fault offset: 0x00000000000017be
Faulting process id: 0x2a34
Faulting application start time: 0x01d0e1b58ce8db4b
Faulting application path: C:\$Windows.~BT\Sources\SetupHost.exe
Faulting module path: C:\Windows\system32\msvcrt.dll
Report Id: 7f1ed623-4da9-11e5-8306-08002700307d
Faulting package full name:
Faulting package-relative application ID:
BTW, how did you get a hold of a MS human, I haven't yet?