Even if the hot wallet offered a better percentage yield for the ETH compared to the hardware wallet. He should not import the seedphrase to the hardware device. It's not worth it. Let him simply unstake the ETH on the hot wallet. Create a new wallet on the hardware device. Transfer the ETH and restake it there.
Ethereum wallet are compatible, if the staking platform can work on hot wallet, it will equally work with any other wallet, doing it hardware or hot wallet can't be an excuse.
If OP can "connect" with the staking platform, he can unstake and then stake again with any hardware wallet.
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Create a new wallet on your hardware wallet.
Deposit some ethereum to your hot wallet, $3 at most to see if the wallet isn't accessible by anyone, if the balance remains, unstake the ethereum and send it to your hardware wallet address, then stake your ethereum with your new hardware address.
Don't discard the hot wallet address and the private key, you may need it tomorrow, sometimes airdrop claim and some free tokens.
Your suggestion is valid and sounds safe, but if I understood what the OP said, he/she seem to have suggested to the friend to unstake and move the coins to the new hardware wallet, but there is a fear that performing the stake with this new hardware wallet might be risky, which is not different from the risk of importing the hot wallet files to the hardware device. I'm not too good with these things, but don't you think staking from the hardware wallet also possess it's own risk since the OP is literally worried about the risk involved?.
If the staking platform is a risk, the hot wallet is not safe in the first place, in addition the staked Ether is also at risk.
It's worth knowing that hardware wallet keep your private keys offline from the internet but it doesn't protect you when you connect to the wrong platform or approve wrong transactions. If the staking platform in question is risky, there is no need to make any connection with the hardware wallet.
I will advice OP to unstake the Ether like I suggest earlier in the above. Trezor and Leger has third party staking platforms, choose one of them and stake back the Ether.