It's not a direct response to your question, but one important fact is that our beefy machines in Fedora Infrastructure are out of warranty now (and replacing them would cost a lot of money, I assume). That's one of the major reasons why they won't be migrated to the new datacenter location, I believe.
Maybe that shows my ignorance, but has the approach of using machines w/o warranty been considered? Most servers seem to work just fine for years and years, and the warranty is mostly useful to catch factory defects.
We've often used machines out of warranty for more capacity where they're non critical services, I suspect part of the issue here is there's a DC move where all of the Fedora infra is being shipped across the US and I suspect (I'm not working on this project) that the cost of shipping EOL servers from PHX to RDU is probably a lot more than the value of the equipment so it likely doesn't make financial sense to do so in this case.