Well joasoze you should not write off Tarth purely because the 3 and and less ability is almost useless. Their ability to settle towns is far ahead of anyone else and their ram longbows are amazing.
and yes I am not even sure if my idea will be effective, but hey if it is then it opens up a very unique playstyle I think.
I guess it would be useful to hear the vision and logic behind this ability. Is my idea on the right path or was it purely meant to give Tarth heroes a boost in the early game before proper armies?
Well, as a race goes, Tarth blows. Their faction abilites are fine, they're bows and their scout ability is great, but you could create a custom faction with those abilities with a better race as a base. Using "Men" as a base would get you henchmen and +10% exp bonus, and you could add the bows and scouting to them.
I really don't use the default nations. And when I design my own, Amarians and Tarth are races I have never picked.
I think the idea would be that you would use fewer, more elite troops.