I wrote a element that can handle multiple files for episerver forms: https://github.com/stilren/EpiForm-extensions
Any feedback would be appreciated
Check it out should you happen to get such a request for a client (tested with Episerver.Forms 4.2.1)
This is a solved problem...
Yes, multiple file uploading should be available from Episerver Forms 4.1.0 (from Update 135, Oct 31 2016)