Thinking about your application for blind people.

Would a scan of the buttons to find the active areas not normally be quite fast running of the hands across the device?

Maybe be having software that rejects presses if the previous two buttons next to the current one were also pressed within a fast time-out would allow you to have the scan ability but then also sense the actual button presses.

Might need to make the scan work from either direction as some may scan left to right and some right to left.

bill