Design and implement a comprehensive Ethereum smart contract for a blockchain-based messenger application. The contract should allow users to save, read, and update messages, while maintaining the following key features: 

1. Message Readability: Make messages publicly readable to everyone on the blockchain.
2. Message Writability: Ensure that only the contract owner can write or update messages.
3. Message Update Count: Track and display the number of times a message has been updated.

Your solution should include: 

- A detailed Solidity contract code.
- A clear explanation of the implementation, including the reasoning behind the design choices.
- Considerations for potential security risks and gas optimization.

Please provide a well-structured and concise response, making sure to highlight the key aspects of the contract's functionality and any notable trade-offs.