You got me looking around on the net, and my understanding got better…

I see that the Tomlinson coupler does indeed allow for coupling lines. That's why it has plates which touch when coupled. The principle of the coupler is more related to the Scharfenberg coupler (which, surprisingly for me, dates back to 1903.

They say that the big advantage of the Scharfenberg coupler is that it can couple at very low impact speeds, and that the additional coupling (air, electric (including fiber optics) occurs after nte mechanical coupling (using an air oparated actuator). Uncoupling also uses the actuator, separating the lines first, and then releasing the mechanical coupling. Interestingly, the European standard for interoperability requires Scharfenberg-type couplers for high speed trains.

About "nullifying the emergency brake application when the train separates"… An automatically operated coupler will close the air lines when the uncoupling sequence is run. When the train gets separated, there is no uncoupling sequence, and the air lines will not be cut (and because there are nowadays always electrical couplings as well, the train management system would immediately get a "train separated" notice, and do what has to be done.

Of the knuckle-type couplers (aka "standard" couplers in the US), the Russian SA-3 can automatically couple air lines. In fact, that was the big selling point in Europe back in the 1970s, when one of the attempts to make a transition to automatic couplers occurred. It was the Swiss federal Railways which were pushing quite a bit back then (the then famous Swiss Express trains were operated with that type of automatic couplers, and still today, those cars (EW III, Einheitswagen III) have them within the fixed sets. The main reason why the SBB was pushing it, was because with that coupler, the weight of the freight trains over the Gotthard line would have been increased by something around 50%, which would have been handled by a Re6/6 double header.