Yeah, blind signers have no security holes....
If you want an example, look no further than Satochip: https://satochip.io
Their cards support any text as a PIN. And the chips in smart cards are almost the exact same as HWW SEs. So all you need is a display.
You can set a passphrase when setting up a seed, and it will be automatically used when you use your full PIN.
Discussion
How is that relevant to the conversation? Put the same chip in a signer with a display.
Are we talking DIY devices or manufactured? Please stay consistent.
We are talking about a manufactured device. A manufacturer can put the same chip in a HWW with a display and I think we both know that was what we were talking about.