So is strength actually bombard units bombard attack?

Because say in a mod I wanted to make a catapult, or a bomber be better at bombarding, what would I have to change?

I think the collateral damage and city bombardment damage are listed completely separately from the strength of the unit, which is only relevant when fighting conventionally.

There's a field in the XML file for bombard units. I don't recall its exact name. It is set to 100 for regular siege equipment (catapult, cannon, and artillery), 50 for Cho-Ko-Nu, and 0 for the tanks which can do collateral damage. This determines the "base strength" for doing collateral damage. I'm reasonably certainly if you changed this to 150 or 200 or whatever, the unit would do more collateral damage, while still having the same base strength.

It's not been tested, but it seems highly probable that it will work.

Arathorn