Another plus of per-patch layouts is that it makes working with patches built by someone who uses a different layout trivial.
If you've ever bought or downloaded patches with for instance 10 stomps when you use 4+4, the only way to even see what's on offer is to change to the layout they use, which means you can't use your own stuff right until you switch it back.
With per-patch layouts, if they didn't come with the appropriate layout already built in, it's easy to do it yourself. Just switch to that mode, then save each of them, then they'd each be in the mode the author intended, without messing up your other patches.