you can use electrum offline with your Trezor but although i have never used a hardware wallet but i have seen people do it. be warned that there will be some complications that i have seen others experience so you might want to try this setup first and see how it works before sending any major amounts to such wallet.

also i would like to suggest a 2 of 3 setup instead of 2 of 2 and keeping that extra key as the last resort for example if your trezor was destroyed and you couldn't have access to your backup anymore that third key cold come in handy.