can you share the link again. i tried to go to that but i got a 404 error for the page.
Looks like they changed the forum name. It's now here -
I can not get the cheats working in WC3 with the "wc3 -mitchell" line added to the file like you posted.
I am probably adding it in the wrong place in that file, but I can't find where to add it properly.
Edit: Finally figured it out. For Wing Commander 3 It is not in the dosboxWC3 conf file. The [autoexec] section is in the dosboxWC3_single conf file.
Add it in after the wc3 exe line.