I thought about doing this with my two eel tanks, putting them in a central location (take up about a whole wall) with a large shared filtration/sump/'fuge.
The only warning I have, and the reason I didn't do it, is that contaminants can then move between tanks. If one tank is ever infected or polluted by something, it will quickly move between the tanks, potentially causing problems in both tanks.
I've never had a tank "crash" and should I ever, i don't want it to be two. Good idea though, I may still do it eventually, just a little added risk.