If the servers weren't made for that, it'd take a lot more work to rework everything and would need an entire overhaul of the system, it wouldn't be something they could do in a week on top of everything else for patches + xpac + graphical update. Finite dev time + finite devs makes this incredibly difficult for something that they didn't intend in the first place to code.
Considering they wanted to add more DCs during ShB and they even said "we tried throwing money at new servers and they just didn't have them," money is indeed not the answer to this. Their main focus is making sure people can actually play first, as that will always be Priority 1, and as I recall they've said they want to expand housing servers once they're done expanding DCs and additional servers. It'll take time and I know no one wants to hear that it's going to take time, but the need to actually secure things needs to happen first before they can do anything more. At the very least I would love for them to rewrite enough code to compartmentalize housing items filesizes to open a couple more wards each patch, but I don't know how feasible that is.