Again, requiring a full node sync doesn't add any value. It's completely pointless and wastes drive space. Just because something is less functional doesn't mean it doesn't have security vulnerabilities, and if security is your actual concern you should simply run whatever client you want offline. For most people, that's going to be MEW since it's very easy to use and set up offline. It's also going to be orders of magnitude more secure than using any wallet synced to the blockchain since that means it's an online wallet.