I think changing the capital will change many thing.
Kathmandu valley is already over populated and polluted. Even to preserve the valley and its resident, Kathmandu should no longer be a capital city.
The new capital city should be somewhere in no mans land, where there is not much facilities or resources. Take an example from United States. they built a new city for Atlanta Olympics in 1996. We should be doing the same.
A well planned capital city, should be something the government be thinking now.