On a V2.2 board, I was getting very close values for no blade and blade 1.
I bridged TX and data1 and changed the Blade ID Class and still get very close values for no blade and this 2nd 7/8" blade I have here (no resistor). So there’s an example where you just need to do it right and use a Blade ID resistor.
That said, if I were to use resistors, I would probably be doing scanid anyway to see what the board really sees and using those values.
So to answer your question, I vote for #3 and just make it part of the setup procedure.
So then a pre-requisite would indeed require adding an entry in blades array for each blade you want to use, uploading, then proceeding with scanning.