We use typeahead fields in a number of our custom forms. Mostly, users know which entry to make - for instance, a typeahead might list all active users in the system; they would only see the names beginning with "A", so it would require the submitter to type a few letters of the user's name to narrow the list to select the specific user.
However, there are times when users might not know the name of an item, for instance, a specific Program name. In those instances they would have to review the full list. However, typeadhead fields are currently limited to 20 viewable items at a time.
We would like to propose that you allow more entries to display. I'm guessing that a 20 item limitation is imposed for caching or throughput issues. Could you raise that limit to 100?
If a field listed every active user in the system that would probably be difficult to implement, but as a fallback, maybe you could add an option for typeahead fields in the custom form setup that would mandate a specific field display ALL items? We only need to see the full list in a few critical fields.