It would be great to be able to set different character limits for each headline field. We limit our homepage headlines to 60 characters whereas the article headline can have up to 110. There is currently no way to reflect these different limits in the Composer UI.
We deliverd this in a recent release of Composer 2.0! You can now set different character limits for each headline type in Composer Settings, however this is only for Composer 2.0 and not V1.
We'll keep this under consideration as we make additional settings available for headlines in the future!