Backstory: Continuing with the hand drawn letter premise... Sending letters overseas is quite expensive, why not let a service send it locally for half the price?
The Idea: A service that sends hand written letters locally.
Deep Dive: You would build a service where someone can upload their letter content, delivery address and select the font/script style they prefer. You would start with your own country and advertise in another country, preferably overseas, offering the biggest savings to your customers. Additionally, you would save time during overseas transit.
Validation: As in the last email, people are already using this service to send commercial letters directly to customers. To prove this one out quickly, you could hand draw the first few yourself.
Monetization: You would charge a fee between the origin country's domestic postal rate and the international rate.