Thanks for the quick response and sorry for the delay in coming back to you. Great news that you are planning to 3.5 this and your other great plugins. Your concept for the chooser sounds ideal and tidying up the variable form would be the icing on the cake.
Icon wise, having a choice like 'atto_generico' would be perfect, as we could then align it to our internal brand. I did have a quick look at some font awesome and something like might also work well.
I'm a little embarrassed I didn't' spot the 'atto/snippet:visible' capability, which is perfect.
My interaction with you and what the direction you are taking this has really strengthened my view that this will allow us to create a whole suite of templates for our course builders, and that it will be an important tool for us.
Thanks again for all the hard work.