Hi,

I made a small mod that replaces Yisha with Karen Stringer from the Canteran Republic. The mod is compatible with the main story and don't alter your save game.

I uploaded it to Nexus mods:
http://www.nexusmods.com/xrebirth/mods/512/?tab=1&navtag=http%3A%2F%2Fwww.nexusmods.com%2Fxrebirth%2Fajax%2Fmoddescription%2F%3Fid%3D512%26preview%3D&pUp=1

So if anyone wants to swap Yisha, just grab the mod.

Have fun!