Today I was looking back at things I tried previously that didn't work out and how to modify them to make them work.

What I came across that was bugging me was making mercanry units trainable.
Initially, I only wanted them retrainable as in this topic:
https://forums.totalwar.org/vb/showthread.php?t=95283

However, as that didn't work out for some reason, I thought of scrapping the limit of only allowing retraining, in making the unit fully hirable.

As you can imagine, that didn't quite work either...

What I did:
Change descr_regions.txt to have several regions have a resource called levant
Change export_descr_buildings.txt to add levant as one of the hidden resources to the top
Change export_descr_buildings.txt to add following lines to large_stone_wall, huge_stone_wall, fortress and citadel:
Code:
                recruit_pool "Crusader Sergeants"  1   0.2   2  0  requires factions { england, scotland, france, hre, denmark, spain, portugal, milan, venice, hungary, poland, sicily, }  and hidden_resource levant
                recruit_pool "Crusader Knights"  1   0.15   2  0  requires factions { england, scotland, france, hre, denmark, spain, portugal, milan, venice, hungary, poland, sicily, }  and hidden_resource levant
                recruit_pool "Religious Fanatics"  1   0.2   3  0  requires factions { england, scotland, france, hre, denmark, spain, portugal, milan, venice, hungary, poland, sicily, }  and hidden_resource levant
                recruit_pool "Great Cross"  1   0.1   1  0  requires factions { england, scotland, france, hre, denmark, spain, portugal, milan, venice, hungary, poland, sicily, }  and hidden_resource levant
                recruit_pool "Ghazis"  1   0.2   3  0  requires factions { egypt, turks, }  and hidden_resource levant
                recruit_pool "Mutatawwi'a"  1   0.2   4  0  requires factions { egypt, turks, }  and hidden_resource levant
Change export_descr_unit.txt to add the factions to the ownership line of the above units
Started a new game as HRE, teleported a character to Damascus, took it after a turn using auto_win, add_population up to 24000, process_cq to build all walls and enough PO buildings to prevent a revolt.
Ended turn about 10 times.

Still cannot hire any of the units.
I tried above then also with removing the mercenary_unit attribute off the selected units, but that didn't help either.

Of course I could create a completely new unit resembling the above units, but it has to be the same unit in my case because I want this to allow retraining.

Any pointers on where I went wrong?