Much like the query function for select fields, you should offer other functions like ASC: or DESC:

This way, if we have large, manual comma separated lists that we want to maintain in alphabetical order we don't have to find where new values are alphabetically and go plug it in the appropriate spot -we can just plug them on the end.

So if we have a list of cities that we service we could have the custom field entry be ASC: Columbus, Akron, Gallipolis, Dayton, . . .

And the form would default the drop down options to display as Akron, Columbus, Dayton, Gallipolis