OK. Doing it modally has so many benefits.
Downside:
• You can't ‘just draw’ directly on a module
Upside:
• You get a full canvas to draw on, pinch and zoom
• Drawing is thus available to finger users and not just Pencil
• You have an undo stack
• You can lasso-select and move things around
• Showing the tool picker lets you use different colors and tools
• Scaling just works — it's just an image, so it aspect fits any size
I think my mind is made up on this one