Changing filesystem resize patterns

Yes.

The prototype I wrote used 100TB as the base address space size so everything in the XFS filesystem is scaled to maximum sizes.
The only thing that takes significant space is 2GB for the journal - 100 sets of AG headers and btree root blocks is less than 4MB of space. However, by maximally sizing everything, the address space can be grown (yes, you can still "physically" grow the filesystem to use all the available device address space!) to a capacity of 10-20PB before AG count scalability limitations start to kick in.

That should be enough capacity for the next decade or so....

-Dave.