Fire ! To force campain fights as opposed to overriding city sieges

Granted, melee units use fire in Civ5, but it's just flavor.

I would like to really be able to switch any unit into fire mode for attacking cities.

The result would be the city would be more or less destroyed after a number yet to be determined of fire attacks.

The thing is, a city would be much more easy to take with fire than without. BUT, the city would be destroyed in the process.

It would then force a defender to fight in campain rather than waiting near his cities.

It may work even better if buildings give virtually infinite bonuses. A little like in this idea http://forums.civfanatics.com/showthread.php?t=475632. The idea is that whatever is spent in hammers has a permanent benefit.

Then, if a civilization, like it's expected to, is highly focusing on science on every of its cities, it may want to avoid one of its cities to burn easily, and go install a defensive dispositif in the campain.

It's an interesting premise.
It would give more sense to surrounding a city.
Up to a certain point where air bridges and refrigeration would weaken the tactic.

In order to initiate :

• burning down parts of city (conquering)
• burning down the city (destroying)
• starvation
• block access to resources
• block access to trade routes
• etc.

A possibility could be to select targets in the cities or randomly burn things down. In case you'ld like to destroy some defensive or military structures. So that you don't have to rebuild your economic and cultural buildings if you intend to capture the city instead of burning/starving it down or out.