OK, I've tested and now the answer is clear. We cannot add the attribute "heir" in campaign script. The script simply cannot go through the compiler.
script:
Code:
spawn_army
faction timurids
character Shah Rukh, named character, heir, (whatever)
(whatever)
end
log:
Code:
00:51:02.738 [system.io] [info] open: found mods/Tsardoms_alpha-0.35/data/world/maps/campaign/imperial_campaign/campaign_script.txt (from: D:\Steam\steamapps\common\Medieval II Total War)00:51:02.739 [game.script] [error] Script parsing error at line 656, column 58 in mods/Tsardoms_alpha-0.35/data/world/maps/campaign/imperial_campaign/campaign_script.txt
Unrecognised character data string (heir)
00:51:02.739 [game.script] [error] Script parsing error at line 658, column 17 in mods/Tsardoms_alpha-0.35/data/world/maps/campaign/imperial_campaign/campaign_script.txt
Couldn't create a script from file mods/Tsardoms_alpha-0.35/data/world/maps/campaign/imperial_campaign/campaign_script.txt