The question isn't whether it is possible or not. For instance, this emulator, had it really wanted, could have used the UEFI API to do networking given the NIC is recognized at UEFI shell.

Doing this in BIOS would require you to implement a lot more from bottom up.

if you are on the bios level you can do anything. But the bare bones nature of old BIOS plus the space limitation of them would make this very difficult.

Now that EFI on the cheapest Staples' laptop is 10x more capable then the most expensive personal computer of 1999, this is not only possible but easy and helped by ton of EFI libraries.