Let me switch the field type on an existing database.
I created a database and erroneously set a bunch of the fields to 'multi-select' when what I really wanted was 'string select.' I've already added things to this database and now I can't change the fields to the type I want without manually re-entering everything. Please let me edit the field type if the data already in the field does not conflict with the new type. (I.e. multi-select data could go to string values or plain text, and if it's string values but all the strings currently in the database are integers, let me convert it to integers.)
Seems to make sense. Of course not all field types would be compatible (how to convert string to integer, fx).
I just ran into something where I wanted to change a field type from Text to "Link to entry" - would have been nice if even that would be possible, perhaps with a search-sync-and-create wizard to make all the "Links to entries" possible.