I cannot tell you about the ride height change. I do not believe that you are doing anything dangerous, but you may not like the ride with the stiffer spring.
If you could get the ride height to be correct at load with the airsprings, why didn't you just stay with those?
Lastly, the only bad part about changing springs as you plan in that the entire weight of the coach will probably have to be lifted by an inch or more to get the new springs into place and yes, it is just a bolt-bolt job most of the time. But be sure you have a good long drift to get the bolts into the springs.
Matt