Depends on who you want to be using it. If it's just for this crowd of hobbyists, sure, that's reasonable. If you're talking about something that could eventually reach out in scope, I think they're not going to want to deal with a deck of SD cards.

Plus, I'd rather have one large (real) file system than 4 or 5 small ones that I have to juggle with things like a union file system, a (fragile) concatenated file system, etc. SSD == simple way to get an easy to manage 64GB+ file system.

Yes. So that it doesn't lose power during storms, doesn't need to interface with a UPS 10 times bigger than it, can be relocated without powering it off, etc.

I've thought about using an old or cheap (walmart special) laptop for that part (battery powered home server). But it would have lots of non-necessary parts, like the screen and keyboard, which would make it unnecessarily large.