Congrats on getting the 12VP rebuilt
I think I would go with the straight gun it the 1-125 at least for a while to see if any ion-burn shows up. (I need to re-read your thread to refresh my memory on how that CRT came to be)
As for the other set, I'm pondering a similar situation myself. Use a freshly rebuilt CRT or NOS CRT in a set that gets played a lot. Or drive weaker / more common CRTs into the ground before swapping them out
