I wouldn’t advise what your attempting for several reasons, the chief being safety. The second code and law.
Although “ground” is “ground”, the paths are important. Im not an electrical engineer by any stretch but I believe what your proposing has the potential to be not so safe for your DC devices.
What I am in a similar situations was convert the 3 way to single pole, put a z-wave switch on one end, rewired to send 120 to the remote and am putting in a HA Switch Plate
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