Does this solve their early castle age weakness to knights? You’d need to have a pretty massive effect to repel knights, especially since this is kinda forcing them into a big, multi-tc boom to stay alive(or else their wood lines and gold would be vulnerable anyway), meaning they’d have little in the way of resources to devote towards defensive units.
Wouldn’t this have a pretty big impact on water maps? They are already fairly dominant on those maps, so by buffing their castles and towers, I’m concerned their water play could become almost unstoppable.
A buff for their towers specifically against cavalry and siege is interesting, I have to admit. That said, that’s essentially what Svan Towers is, and that’s rarely used just because towers are too expensive to really commit to in early castle age. Plus, lacking ballistics, it would have a hard time being very effective against cavalry even with a big damage bonus.
You could give them free ballistics, I suppose.