Unfortunately, you cannot do anything with the stock/default keyboard. You'd have to jail break. Then, for now, the jail break tweak that we all got accustomed to using, 5-Row Keyboard, has not been updated for iOS 5.x. So, we are all waiting for an update (or an iPad-compatible edition of iKeywi). So, even the jail breakers are SOL.
Yes, there are apps that have various different keyboard keys. However, you can't set those keyboards as the default. The best you can do is type with the app keyboard and then copy/paste the text over. As of now, there is no way to use any other keyboard than the default in the stock Apple apps.
So, ultimately, I was of no help. But, now you know that, for stock, there is no way. And, for us jail breakers - we're waiting. Sorry to not be a better news bringer...
Marilyn