Ultimately when you move to a new DC you don't care where cables were going. You care where you want them to be attached to in the new DC. You don't want to replicate the mess, rather to know which LANs/VLANs your servers need access to, so you have some planning to do, but the day you unplug everything you don't have to mind where the cables were going.

I've seen more hard drive than PSU dying in datacenter move, which is usually solved with having a few spares and good backups, obviously external from the datacenter being moved. But same can be said of PSUs. Obviously the more heterogeneous your servers are, the hardest it is to have spares for everything. Everytime we did some DC moves, we used that opportunity to replace a few old servers which meant we bought a few spares. The big question is if the Xen project has the financial capacity to buy a handful of servers.

Let's keep in mind we are talking about a relatively easy move. This might be inconvenient for the DEVs but this is an infrastructure (CI) that is not customer facing and that can survive being offline 2 or 3 days. Users can still download the deliverables, developers can still code in the meantime.