I recently tried the new option in Windows 10 that allows to create a „virtual surround“ sound via Dolby Atmos for Headphones (there is a 30 day trial). I was very skeptical at first, but the mix created while playing back a 7.1 source in Plex on Windows was impressive with very good positional audio. However, since Plex will transcode to 7.1 PCM you never really get a Atmos mix which I imagine would be even better.
Thus, my suggestion would be to include Dolby Atmos for Headphones as output option in Infuse. You could even correctly decode the original Atmos stream and create a proper Dolby Atmos for Headphones 2ch Output. I think this would be the first and best implementation when you connect Headphones to the Apple TV.
(The Windows add on costs money so there will probably be licensing involved but I would gladly pay 20 bucks in app purchase if that gets me proper Atmos headphone surround.)