I'm putting together a mod to do some experimenting and this was on my list of additions too. I'll go through the tutorial myself and see if I get the same problem.
Actually, I've made some unit_prod and build_prod changes already. It's a bad idea to change too many things at once before a test session, so I'll have to come back for this later.
Here's what I've done so far.
1) Copied the entire MTW:VI (with king-death patch applied) directory
2) Pasted into the Total War folder and renamed the copy folder.
3) Run Gnome editor to alter the unit/build prod files.
4) No changes to startpos files yet.
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