These are the only TYW leaders I found that can be promoted.... let me know if there are others...
TYW promotable leaders mdl list
220 HRE Gallas
222 HRE Von Hatzfeldt
233 HRE Marradas
256 SWE Lennart Torstensson
262 SWE Alexander Leslie
273 FRA Turenne
278 FRA Enghien
Drop box link to zip with edited files that should fix promotion issue ..... Special thanks to Bohemond
https://www.dropbox.com/s/cwhxkq6bvk59z ... s.zip?dl=0
Replace the 7 files in the TYW/gamedata/models folder with the 7 edited files from the zip. (There is a folder with the originals to revert in case I messed something up).
Then delete the Models.Cache file. The game will make a new one when restarted.
I hope this helps...