Increasing Barbarian's cities to max level

I've read some tutorials on how to include Barbarian cultures' cities and buildings to maximum level, aka. porting barbarian from BI to RTW 1.5. But I have no luck because there is no tutorial on how to generate descr_items.db that I know of.

However, I don't really need all the extra buildings from BI for my mod (RTW:Alexander, so similar to 1.5). What I need is just to increase barbarian culture's ability to build large_city and huge_city. I know how to make the strat models appear on the campaign map but I don't really need to change the city layout in battle map (yet).

Anyone can give me tips?

Thanks!