Really interesting project. I am working in a similar one: I recycled the famous Aqara door sensor and soldered a generic cable extended door sensor from Ali. Has been working like a charm for +1y.
My main problem is that my gas counter is outside, separed 5-6m from my house. It worked well from some motnhs relying on a repeater in a plug that was in the outer wall of the house (but inside) but since then connection has become unstable and I lose connection, but this got solved adding a flashed Sonoff ZBDongle-P with router software kept in the middle (in a precarious way).
However, had to move the location of the dongle to get it protected from rain and the problem is that has to be attached close to a metallic fence (between my house and the neighbor's). Since then, Aqara temp-LQI-batt reports go well, but I lose almost all impulses except when i open the counter's door (problem, the door is on the street so this is not a solution). How did you manage to get the ZB sensor outside? Can you share a diagram or a photo of you current setup? any innovative ideas to ensure transmission?
Thanks