I just got BtS a week ago, and I've noticed the change in inflation, even though I haven't gotten past the medieval age. Since my friend and I do quite a bit of minor modding, we went into the xmls and found that the inflation rate was 150% of what it used to be in vanilla and warlords. Go figure.
As for my opinion on Corporations, they should not be used as a weapon, and they should give a benefit in pretty much any city it's placed in. Look at McDonalds, Microsoft, and Starbucks. They're everywhere, and you don't see nations' economy's crumbling because of it.
A corporation should be beneficial even if you don't have the corporate headquarters, just like a religion is. My solution would be to lower the maintenance cost by maybe 80-90%, lower the +

to the headquarters to +1

rather than +5

, and revert the inflation rate back to pre-BtS rate.
The problem with that comes with the benefits of corporations. For such a small amount of maintenance, are the bonuses from the corporation too powerful? I honestly don't know, since I haven't gotten far enough in a game yet.
What would have been really cool, is that if the maintenance cost was variable, depending on the number of resources consumed. That way, smaller nations with less resources could still reap the benefits, although less, but pay less maintenance because of it.