Wonderful Idea. I would request the idea of Colorways in a dark color, some muted colors to go with other bed decor.
The outside of the mattress is a predominate feature now, and the point is to have a beautiful neat bed.
Blending with the sheet would take it up a notch. Also, if your target audience is the Eldery and those who can't lift a corner, your price point is off a bit(AARP discount for them?).
These are for Everyone too, by the way I'm gonna dye mine with Rite plus and I bet that will look great and match my sheets. Again, clever idea, and as a pocket for stuff is a great bonus. Kiss for Grandma.