They key to replacing Highmore and Gaudette in our lineup is special teams.
Gaudette is much more replaceable on the PP, with Stutzle, Tkachuk, Batherson, Cozens, Giroux, Perron, Greig and Zetterlund clearly ahead of him at FWD and Sanderson/Chabot always manning the backend. He is pretty clearly the next man up, and I am not sure there's a comparable option, but I suspect we could get similar results from just riding the "hot hand".
Amadio seems like he could take on more of a PK role, but I am not sure they have anyone they feel really fits that role. Giroux, Greig, and Pinto are our three main guys, but Highmore has been used as the next forward up by a pretty large margin.