Sounds like you have the flexibility you need for patching then.
In future personally I think most people will be simpler to have everything managed by the router itself since you can see the incoming calls listed there as well the paired handsets, name the handsets, and optionally set things like time ranges for which phones will ring incoming calls at what times of day.
However I would understand if you want to compare the answerphone features before deciding, and I know some people also have become used to call barring or call screening features on their base stations.
Fortunately you don't have to decide any of that on the day of switchover if you do go down this route and retain your own base station meantime.
The main thing to avoid is inadvertently backfeeding the FON output onto the external telephone line since having two 48V supplies fighting on the same copper pair does not go well, and the PSTN voltage from the exchange (and dial tone) is not always discontinued immediately or even the same day.
However it sounds like you have that aspect covered too and understand the separation.
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An aside, over in the Home Networking forum their are recurring conversations about people putting a small switch in a central location for patching (sometimes the loft or a cupboard under the stairs) which makes wired devices less dependent on a fixed location for the router itself.
If I had my own place I would probably be going down that route as there is not much sign of new builds including ethernet cabling to all rooms as standard, especially now that there is such a trend for "Wi-Fi all the things" and "oh just add a plug-in booster or mesh system".
prlzx on Zen: FTTC (VDSL) at ~40Mbps / 10Mbps
with IP4/6 (no v6? - not true Internet)
Edited by prlzx (Mon 19-Feb-24 22:26:57)