here i suggest the addition of new siege units

Ram
Str 1, Move 1, Hammers 25
+200% vs City
Bombard City 8% (BTS), when bombarb, wall and castle dont provide protection bonus against this bombardment
Enable by Construction

Siege Ram
Str 2, Move 1, Hammers 50
+200% vs City
Bombard City 12% (BTS), when bombarb, wall and castle dont provide protection bonus against this bombardment
Enable by Engineering

Bombard
Str 9, Move 1, Hammers ? (Average of Cannon and Trebuchet)
Bombard City 12% (BTS)
Enable by Gunpowder, Replaceable Parts

Yes! I have always wanted a bombard! Perhaps with the Basilica as the new Ottoman UU?

Bombard
Str 9, Move 1, Hammers ? (Average of Cannon and Trebuchet)
Bombard City 12% (BTS)
Enable by Gunpowder, Replaceable Parts
I like it.

I remember the Bombard from Double your Pleasure for Civ III :)