i know this might sound strange but i was wondering: are there internal miniPCI/express cards that can be used with pfsense? or at all?
considering how terrible many consumer routers are, i would really consider adding a VDSL interface to a pfsense box to use as WAN so that i'd have a proper firewall routing device for handling my small network.
Pretty much no.
There are some cards that can act as an internal modem though they are ADSL only as far as I know. In reality they are a complete modem/router chipset on a PCI card. They appear as a network interface to pfSense and you would configure them exactly as you would an external modem.
I guess it depends on your location but many people would never use internal modems due to risk of line surges toasting your whole firewall rather than just the modem.
If you really want a single box setup your best bet would be to remove a VDSL modem from it's box and mount it inside your pfSense box.
Check out this new card…
There are external VDSL modems that act as modems only and you have a bridged connection to ISP's network. Such as this one: