1. A first line playing 20 minutes a night while losing their matchups is not a good line. It's not even a decent one - it's bad. Breaking up that line should result in an improvement by itself.
2. X-Perfetti-Niederreiter is probably the best shot we have of internally replacing Ehlers' impact without acquiring a direct replacement. That alone requires Arniel to rely on Perfetti as the 2C, to break up the third line and weaken it to a degree, and for Chevy to find someone to complement 91 and 62 on that line - preferably someone with some scoring threat. And even then, that severely weakens the third line, since Nino wouldn't be on it anymore.
3. Whoever they choose for the 2C role is going to be a risk. The thing is, if you get rid of Ehlers, you're not going to be equipped to manage the situation if that risk materialises.