I think I would go with DECT for the handsets with dual mode PSTN+SIP base unit, with the main base plugged into a switch or router without needing the CW1308 cabling.
UK DECT being sub-2GHz has a bit better range through walls than Wi-Fi especially with lower data rate requirements, and GAP providing vendor-agnostic compatibility.
I only mentioned the adaptors as those 10/100 looked relatively affordable (compared with gigiabit over coax or TP), and I don't know how much people pay for ATAs these days for comparison (are they usually second hand?).
I expect come the switchoff, ATAs will be what suits a minority but significant segment of the population wanting to use the same phone.
By analogy with the digital TV switchover, STBs were used to achieve the take up where people didn't want to replace all their TVs, and for people with VCRs or DVD recorders (commonly still connected over SCART even in 2009).
But I have a feeling most households will be using mobile (with or without Wi-Fi calling) in combination with ISPs offering a SIP package (as a line rental replacement) bundled into the fibre Internet monthly billing.
Enough people will want to keep the same geographical number at least for the first few years, even if it is automatically ported into their ISP such that they can also carry it with them on an app when out and about.
prlzx on Zen: FTTC (VDSL) at ~40Mbps / 10Mbps
with IP4/6 (no v6? - not true Internet)
Edited by prlzx (Thu 10-Jun-21 23:21:16)