Hi capbenedict,
If you replaced the emergency exit window you'd be creating a serious safety issue. If a fire prevents you from getting to the door, you'll have no way out of the coach. While not all that common, RV fires do happen, and the fire spreads pretty quickly. You could need that emergency exit one day.
You might also be creating a resale/trade-in problem for the future.
I doubt very much that Heartland or the window manufacturer would be willing to help you undo a safety feature.