I don't trust the RNG in any signing device (HW) and in general I think it's bad security practice for anyone to either.
As much as I appreciate a good level of paranoia when it comes to Bitcoin security, I don't think this is practically necessary. If you use dice to create a seed phrase, how do you sign a transaction with your hardware wallet? I'm thinking about for instance
Reused R values: how do you use dice rolls to avoid this?
I use 100 dice throws ~ to generate a key.
I'd say you're a few bits short this way. I was thinking of 100 coin tosses. With 100 dice throws, you'll have enough entropy.
Since standard practice should always be to test recovery using seed words then the checksum isn't necessary.
The checksum is part of user friendliness: if a user makes a mistake in entering his seed words without a built-in checksum, he restores a different wallet. That will leave the average user puzzled (and panicked), and can easily be avoided by a simple: "wrong seed, try again" message.