Honestly, the solution is to wait for ES6 'let' scope - CoffeeScript's scope issues exist because it is, by intentional design, similar to JavaScript, and JS has scope issues.
When ES6 is a viable option, CoffeeScript can incorporate lexical scope in a backwards compatible way, and its scoping will become much less unexpected.
why wait when you can use it today with 6to5 or traceur? obviously you'll need a build step, but if the app is larger than tiny, you probably already have one.
When ES6 is a viable option, CoffeeScript can incorporate lexical scope in a backwards compatible way, and its scoping will become much less unexpected.