Hello!

First of all you will spend additional time to upload video 3 times (upload to the server, then upload to another server for transcoding, then to upload back on your first server). 

Second you need to have trancoding mechanism on the seconds server, because you can not run transcoding tool from your first server with Una on the second server. Also when transcoded file is on your server, you need to make special changes in database to register the file in Una tables.  

Anyway, this issue requires development and research to find the best solution, but may be it would be better to optimize trasncoding on your site using original tool.