Dave, I've previously seen a post somewhere on here about this and as far as I remember it WAS possible. I'm assuming a 2 gang T1 will just need the one neutral wire supplying it with a constant feed of power (even if it doesn't you should have a neutral on each gang feed in). I assume you'd set a scene...if condition is master device T1 2nd gang "on" then perform sonoff basic (eg table lamp) "on", and vice versa for off. T1 1st gang would just be to your normal ceiling light.
Please note...the above info is all theoretical and should not be relied upon whatsoever!!
Hope this helps!
That was I was thinking, Thanks for the reply
It should work. I tested similar scenario. Have you implemented it ?