Peter has a number of issues that prevent that solution as he has mentioned here before.
He couldn't persuade his group to get the right and slightly more expensive Garmon transponder so piping PAw into it for ADSB isn't currently possible.
With the SkyEcho I am guessing he's doing this as a personal purchase to avoid other members unwillingness to invest
I trust Peter will forgive me if I have this wrong
On your solution, have you ever been in an aircraft with PAw alerts direct from the box rather than filtered by SD? It would not be a route I would take.