I'd like to buck the rest of the thread on this one.

If you want to play a defensive game... try Prussia.

My current Prussian campaign, I decided to do something differant... and not declare war. I was going to see what happened when I played as the Prussians and only fought defensive wars. Whenever a nation would declare war on me, I would raise an army and take thier lands until they no longer existed. Between wars would be periods of peace lasting up to ten, fifteen years during which time I would dissolve most of my forces other then garrisons and a standing army or two, and during those peace periods my treasury would do very well.

As a result of this VERY unconventional approach, my expansion has been defined by those whom have attacked me. The year is about 1747 (playing prestige) and I have taken all of Denmark, Hanover, and Sweden. My economy is very healthy, and I have over fifty years to take out Courtland and Poland and move into France for the win (although the Maratha is going to be tough to out-prestige)

Give it a try - Prussia, and only fight the nations who declare war on you.