Reading through I was excited when you made clear all the advantages and the necessity of CBDC in your community, but then just I was getting a grip of it, you dropped the bomb, and I was like woooh!
Very true, CBDC is a very good initiative if properly managed, but at same time it comes with its risks like the example you gave.

where a grandma who sells in the market wants to get paid by such means and she gets scammed or she makes a mistake while purchasing an item

So like you, I don't think its implementation will solve such headache but maybe in due time. Good luck in the contest.