We currently have home phone wireless with the Panasonic handset, which is... extremely basic, to be polite. I've just found mention of a white box that you can plug your own phones into, on a 2009 forum post.
Are these still available? Any better description than "white box" which is difficult to google?
Its the vodafone at home box, often come up on trademe but I always ended up with GSM buzz on the call unless I used the external antenna which most people seem to have thrown out when setting it up.
And the echo, and the lack of immedate dialing that the panasonic gives you.
You _should_ be able to register a less primitave handset to the panasonic as it is just a dect phone. But I dont know if its abysmal range is a problem with the handset or the base, so it might not gain you much.