I don't expect any provider to support this kind of setup, or even admit it is possible. I believe that is fine. They sell a mass market service. Supporting anything non-standard is expensive. So they cannot publish anything which could be misunderstood as "you can use your own equipment".
That doesn't mean that it won't work.
My only experience is with a local provider, with a similar looking setup. They use a pretty standard BX (single strand bidi) SFP in their CPE. I am using it in a GS1900-10HP with OpenWrt instead. The provider splits Internet, TV and management/phone into 3 VLANs, so the SFP port must be confgured with the correct VLAN IDs. I only have Internet at this site, so I only needed one of them. But it still has to match the provider of course.
Figuring out which VLAN to use, if any, might require a bit of snooping. But you should be able to do that using the switch. If the providers CPE has RJ45 WAN as an alternative, you might even be able to put the switch temporarily between the fiber and the CPE to inspect the traffic.
I have no idea what Vodafone does, and it this is relevant at all.
The cases I can think of where this wouldn't work is if the provider makes their network config depend on CPE management somehow. E.g having only an open management VLAN be default, and then enable Internet service etc after talking TR069 to the CPE.
They could also have some mac-address filters, but you should be able to work around that by cloning the address from the provider CPE.
EDIT: wrt the size of the complete installation - I posted a picture of my setup a while ago: Searching for router to buy - #38 by bmork .The GS1900-10HP with the RPi4 attached is physically smaller than my provider's CPE.
You don't need those USB UART dongles of course - they are just there for debugging.
I have two Unifi 6 Lite APs connected to, and powered by, the GS1900. Both are configured with two SSIDs - one for IoT and one for more trustworthy devices.Using VLAN tagging to split the different layer 2 network segments, so that the Internet WAN VLAN from the fibre goes to the single RPi4 ethernet port along the VLANs used by the APs, The RPi is both router and "server" in this network.