if you use Data Assist to create the forms, you can set up the file upload in the Data Assist wizard.
if you are adding the file fields after the fact, then use the DW menu to add the file fields and the encoding type will be taken care of for you.
if you are adding the file fields manually, then you need to set the encoding type manually.
if you would like to make a feature request, please post it to the product Suggestions page:
http://www.webassist.com/community/feedback/dashboard.php