Belgian superstar physiotherapist Lieven Maesschalck, (who treated sportsroyalty such as Wout van Aert, Eden Hazard, Luca Modric, Frank Vandenbroucke, Johan Musseeuw, Justine Henin...) where Remco is currently rehabilitating, says he is amazed by Remco's progress and has no doubt he will come back stronger than before. Can't tell you more, since the rest is behind a paywall
I don't know if W/kg is really the question. In Burgos he was still 2kg above his goal weight. For a rider his size, that's a lot of margin at 61kg. Summer 2019 he said the lab results of his then latest FTP said he pushed 450W. Assuming that is over 20 minutes, then he should theoretically be able to push around 427W for an hour, which is immense for his weight. Your theory was actually put to the test in Burgos, where the lead-up to the climb was raced hard in the crosswinds, and all the skinny climbers were completely dead. No Kuss, Sosa, Yates... to be seen. They all cracked early on the climb.