Allow to add more than one product variation per webform

When I:

1) create a normal entity select element in my webform with one allowed value, and
2) populate the choices in that element from a view list of product variations, and
3) create a webform commerce webform order handler that selects "Product variation from webform element" referencing the element I just created

Then everything works fine. The product variation is added to the cart. Trying to add multiple items to the cart from a single webform element fails in various ways.

* Using entity checkboxes, entity select, etc: using the same procedure as above, only difference being multiple allowed values, then I get *something* in the cart - but not one or more product variations. What does happen is there's a new row, a number in the quantiy column, a title if I've overwritten it but otherwise blank; but nothing in the price columns.

* Using entity radio, and entity select and more than one value checked, you get a "problem occurred with the website" error.

* Using a normal select element with the product variation values entered in manually with 'custom options' works with just one value selected, but bombs with more than one.

Could do more testing to map out all the ways it doesn't work with multiple selections, but the essential thing is that I can't figure out how to get more than one product variation per webform element into the cart, and the module fails in a couple different ways if you try.

So, is there any way to add multiple product variations to the cart from one webform element that I'm missing? I know I can use multiple webform elements and handlers to accomplish the same thing, but it'd be a lot cleaner if I could do just one of each.