Yes, it's unlikely that a modem would require more bandwidth than the ISA bus provides. Also, most PCI modems are Winmodems which rely on the CPU to do most of their work, so ISA modems are usually ...
Mount an external aerial and feed the cable inside to a sim router that then acts as a backup (maybe primary connection?) to the Vodafone wirless modem/router. I'm guessing this is feasible but what's ...