Couple of years ago, with the need for a quick prototyping setup, I created a very basic PERL script for removing non ASCII characters from a data file, that I wanted to upload into BW. This script helped me get around those upload failures typically associated with special characters. This is especially handy if your sandbox BW installation is not Unicode enabled.
I had shared this script with colleagues and partners who have used it for prototyping, proof of concept (PoC), demos etc. They found it useful. It makes my life very easy, especially for those characters which cannot be RSKC escaped. Pls bear in mind that this is not solution meant for production usage.
Assuming no knowledge of PERL, I have listed out the steps you would need to follow, from start to finish. I am also assuming a Microsoft Windows based OS environment.