That seems like a reasonable idea but I strongly prefer "installation device".
I have not looked up the reason, but "installer device" sounds very jarring
to me as an English English first-language speaker.
I wonder if this works for cases, where the installation medium is a CD or DVD?
Do people know what is meant, when you talk about the CD as an "installation
device"?
Is a CD (the optical disc, not the device file under Linux!) known as "a device"?
I am not a native English speaker, but German.
At least in German I think that would not work.
This proposal is to find a coverterm for all installation mediums: CDs, DVDs,
floppys, USB sticks, ISO files within virtual machines ...
This approach should have higher priority than grammatical refinements IMHO.