Sending a user command to switch microphones might currently possible.
However you would most likely need to create a batch file that does this and trigger it with a user command.
Also I don't know the exact commands you would need to place in a batch file.
I'll add this to my to do list and play with some code for a hard coded command argument.
You may run into CPU difficulties running both BlueIris and iSpy on the same machine unless you have a very fast PC.
Even then it could bog down recording.