I'm not seeing the Tacops coming in another caliber on Sig's website but I imagine it's only a matter of time, I hope.

Just as the title says, I'm looking for a 320 in the carry frame, FDE, threaded barrel with suppressor sights and/or the Romeo reflex in something a little more potent than 9mm.

Went to my LGS today and picked one up today after all the chatter and liked it. I was most comfortable with the carry sized frame. I would say the Romeo Reflex sight being exempt isn't a deal breaker, but I would would want a minimum of .40, threaded barrel with suppressor sights.

Does such a thing exist?

Right now the RX is only in 9mm in full size or compact size. You can get the compact and get a carry size grip.  My guess is you won't see other calibers for quite some time.  Good luck fining a threaded barrel