Re: I don't think FlashSystem can do anything unique.
you've got the right sort of idea, but I think you've made it sound like a negative, which I'd disagree with.
Spectrum Virtualise (what used to be called SVC code) runs on a variety of controller "engines".
If you want to use it to enhance* a large estate of existing (perhaps heterogeneous) FC block storage you'll likely run it on SVC nodes, if you want some of your environment to be AFA you'll likely have V9000 (there's a licence cost saving in most cases), if you want a midrange array you'll most likely go for a Storwize V7000 (although a lot of V7000 customers virtualise FlashSystem 900 too). If you want low cost block storage, the V3700 and V5010 are there for that.
Given the common code base, you can replicate between different members of the family, which is good if your DR doesn't need to be as fast or big as production. Just pick the "engine" or "engines" based on your performance/capacity/function requirement.
So, you are correct when you say "if you really want SVC you don't have to buy Flashsystem", but you've missed the point that amongst AFAs, that functionality is unique.
If you don't like SVC, that's fine! Get yourself along to one of the Flash events IBM are running at the end of the month (I'll be at the one in London) - you'll probably like what you'll hear.
*"enhance" could include enabling existing kit to stretch/hyperswap between sites (or just normal replication as sync/async/async with snapshots), be realtime compressed and/or encrypted, pretty much irrespective of the backend storage (which is nice if you have a heterogenous environment following an acquisition). Having a "legacy" also means that you can work (and be supported) on OS that are also legacy - not many AFAs can do that as they tend to only support what is mainstream when they're designed/launched.