Rule for requiring types for fn definitions only

One of Flow's goals was to provide an 'incremental' model, where users could incrementally migrate their code. As a user of this module, I have faced an overwhelming number of issues with the current "flowtype/require-parameter-type" rule, which throws an error on every missing declaration. A rule that would complement flow's goal of 'incremental migration' would be a separate rule for requiring types for function definitions.

Ideally, it would do something like this:

function example(number) {  // <-- require types here
  return new Promise((resolve, reject) => { 
    resolve(someArray.map(each => each)) // <-- DO NOT require types here
  })
}