What I did:
1. I created a custom Bowcaster, put the File in Override, tested it, it worked. ID: g1_w_bowcstr001
2. I added the normal Bowcaster (g_w_bowcstr001) to the Inventory of all 3 Versions of Suvam. Saved the Files.
3. I used kgff.exe from this Video to change the Bowcasters ID from g_w_bowcstr001 to g1_w_bowcstr001.
4. Moved the suvam01a.utm, suvam02a.utm and suvam03a.utm to the Override.
5. I loaded my Save where I didn't visited Yavin after getting the third Starmap.
6. Traveled to Yavin, triggered the Cutscene, tried to buy my Bowcaster.
And then the Bowcaster wasn't there. What did I do wrong?