that is exactly what people have been suggesting. the link between the HFC modem and the router (not a modem) at the other end is ethernet, not modulated signal - it will work fine as long as you can house and power the switch appropriately. the only other suggestion I can offer is a VDSL link extender kit which will work over much longer distances than you are talking. they are not cheap though. https://www.ple.com.au/Products/620164/Startech-VDSL2-Ethernet-Extender-Kit you're probably not far off the cost of a preterminated fibre cable and a couple of media converters there. apart from the aforementioned halfway switch, no. if there was, the whole world would be using them.