Nip-46 does

Client <--> public relays <--> Signer

And instead you are saying that it should be

Client <--> Signer

So you remove a roundtrip. For the authentication, the easiest to code would be the client sends an event signed by the employee key, signer validates signature and rules, and returns the same event signed by the company key.

Using traditional auth is going to be I think more complex and less secure.

I could build this with rely relatively easy