Sappers change idea

Hi! First of all I am making these change propositions to make my own mod better and I want to hear other peoples opinions.

So Sappers is rarely researched tech. It costs a lot of resources and Villagers are better of working. Also the effect on wood cutting doesn't justify the tech either. Simple discount to 400f and no gold would still not make the tech more useful so I considered changing it a little. In my mod Sappers (in addition to attack bonus vs Buildings) gives Villagers 3 attack bonus vs Siege and +20% repair-rate.

Idea is to make Villagers able to defend Castles especially vs Rams and also to make them more useful in attacks as they can repair and destroy Siege better. While they already are in the battle field they could also use the building attack bonus more often.

What do you think? Is it too good or stilm useless or just too expensive? My goal is to make the tech situationally useful so that you would sometimes get it, but sometimes not.