Thanks, guys. You both assumed correctly: My goal is to free up tracks on the Neo. I figured, if I could get a good submix with the Mackie, there'd be no need to keep all the individual drum tracks. An alternative is, I might run the kick mic direct to the Neo, to give me more permanent control over that. And then just use the Mackie to submix the rest of the kit.
In any case, thanks so much for replying. A little voice in my inexperienced head kept wondering whether the electronics would work, with the setup I was imagining. Nice to know the concept is workable.