Wow thats a lot of arbors.
I survived for around 50 years with just two until recently. one arbor had a grinding wheel and the other end was sanding disks that I swapped, the other arbor at the far end of the shop was the polishing disks, lots of them with various oxides and buffs that could be swapped.
I recently upgraded and bought some soft wheels and because I wasn't sure which way to go a few expanding drums as well, half way through building the arbor I decided to complete the set of soft wheels which meant I had spare expanding drums and belts, so another arbor required and a full set of drums and belts there as well. I am loving it, for some reason I seem to prefer the expanding drums, no idea why I just use them more.
I am still mulling what to do about grinding wheels, I have a 80 sintered for roughing out and a 600 plated on an old arbor, I badly need a 220 in the mix though. (I have a badly worn 220 that I can swap in but it's nearly useless) I have a feeling I will end up with two grinding arbors with 80 sintered and a 600 and another arbor with a 220 diamond perhaps plated perhaps sintered, with a 220 Silicon Carbide on the other side, I shape the SiC wheels for doing oddball shaped things with.
A super grinder would be good, I have the blades just that it's another arbor, possibly a portable one so it can be dragged outside.
I find a surprising amount of material doesn't polish as well as I would like with just diamond so still use the assortment of buffs I have accumulated with various oxides, not everything, some it's the other way, get a decent shine with diamond touch it on the oxide and have it horribly undercut, start again.
Leather, canvas, felt, wood, with Tin Oxide, Cerium Oxide, Aluminium Oxide, Chrome Oxide, thats a lot of buffs. So there's another how many arbors.
Saw blades? depends what you're cutting, opals, faceting material, other expensive stuff get some of those really thin Chinese blades, they are cheap as chips but no good for tougher stuff.
What other blades you get really depends what material and what size you are cutting, lots of options.