You can use metal and plastic in the same rifle if you're willing to make the already rough action worse and risk occasional Jams.
i have 5 original mags, 3 plastic and 2 metal. They will work in my PF18 after about an hour of fine tuning of the pawl alignment.

Pretty sure this falls into the Could vs should.

yes it's possible, but not worth it. mags come up on the sales section here quite often, pick up a few of either type.