Turns out I'm an idiot, and you can totally use a SC5000 player without a mixer to sync videos in Resolume. You can even use two players. Just connect the Resolume computer and both players via a router, and both players will pop up.
Of course you won't be able to get the fader info to use the fader automation, but you can disable that in the clip panel.
Sorry for spreading misinformation and crushing dreams.