If you have a field on one content type, you can easily add it to another content type using the 'Add existing field' option. This is great, and the fact that they can have different settings is cool too (e.g. 'field_image' on a post can save to 'files/blog' and be a large size, while the same field on a client content type can save to 'files/clients' and be a smaller size).
However, there are times when it's necessary to have the same settings for a field across all content types where its used (e.g. an ID number with certain min/max values, a postal address restricted to the site's country, etc.).
In this case, it'd be nice not have to manually copy over all the settings each time a field is added to a new content type. I'd therefore like to suggest a way whereby settings from another content type can be copied over with a field. These can then be changed for the new content type if necessary (i.e. nothing needs to change database-wise), but it prevents the same settings needing to be copied over manually.
I'm not sure how to implement this or what the UI/UX would look/act like, but thought to put the idea out there...