Hi David -
I hear you - that's a tough one from a system level. Because the whole Mag+ architecture is designed to allow you to create content that is native to the canvas, pinching and zooming will actually break that (ie, you'd have to scroll around to see all the content that you can then scroll). The one way we have discussed enhancing this is to make each box or group individually zoomable - similar to how it is done now with the Feature Builder, but native to the plug-in rather than having to step through HTML. That way if you really wanted to, you could do a B-layer only design and make the whole page zoomable.
However, I would strongly discourage that as our user testing has shown that >having< to zoom to read something is a very bad user experience. If many of your customers are asking for the pinch and zoom, it may be worth taking a look at the page design to see if maybe some text elements are hard to read as is.