Caseta Dimmer 3-way circuit with remote dimmer or switch

I am replacing a dimmer in a 3-way circuit with a Caseta PD-6WCL dimmer. I would like to use a wired remote dimmer instead of the PICO remote. Is this possible? If so, what remote dimmers work?

If not, how about a remote switch? To what dimming setting will the remote switch enable when it turns the circuit on?

If not, how do I terminate the unused wires behind the PICO remote? (There are for wires: Black, Blue, Red, Green)

Thanks for any advice.