Just add TCs to castles and towers. The main reason why that UT is considered useless, is because celts lack bracer, and so that final +1 range on buildings.
TCs don’t suffer from that, and having a bit more attack output against late game hussar raids would make the UT more worth to grab.
If celts lack architecture maybe there is a reason…
Not how it works. Basically, to add an arrow, you need to have enough units until you reach the building attack or more.
Also, in mid castle age it would be quite useless, since towers aren’t that common anymore, and you don’t garrison archers in castle just to get more arrows.
Which would also lack that last +1 range, so they would suffer from the same problem of their castles.
Which wouldn’t be that original if there are already UTs doing that…
No, but that wouldn’t be that big of a buff… TCs that deals a bit more damage in late castle age isn’t that big of a deal, and probably the UT cost would be increased a bit too.