The dark plank in the middle was the original structural member, with a vertical plank holding the faucet in place. I put the 2x4 on top in, with screws, then screwed the original plank to that.
Two more little chunks of 2x4 provide a spacer and platform for two straps holding the faucet assembly in place. It's solid as a rock now, which is good, because I'm no expert, but I'm pretty sure that having the CPVC in the basement support the weight of this faucet assembly would be a Truly Bad Idea.
Incidentally - further support for my "late standpipe" theory; the coupling on the hot water matches that on the cold, but with the standpipe there, it can't be turned. So they put on the little angle stuff under it, and there's a second coupling about 4 inches to the right, now. I rest my case.