Torus-shaped fuel tank functionality/design

[Fiwithwings]

Originally Posted by M2dude

The real crunch however, was how to arrange pneumatic services from an APU: Tank 11 was directly forward of the tailcone, so this would have meant either ducting the pneumatics THROUGH the fuel tank (not a particularly good idea )

I'm quoting from the earlier thread about why Concorde didn't have an APU. I know just about nothing about the functionality or design of fuel tanks, so I'm just wondering - what are the reasons against having a torus-shaped fuel tank? Obviously not necessarily a perfect torus, but I wonder why it wouldn't have been possible to simply manufacture a fuel tank of whatever shape with a donut-style hole somewhere in it to allow the hydraulics to safely pass through the middle of the hole? I guess there's some reason about what a fuel tank does that means this isn't done, and I'm curious as to what it is.

Thanks!