I can recommend Paul from
http://www.alpineswitzerland.com
He knows the real estate market in Valais extremely well and is an expert in property sales to residents and non-residents. He deals with all property types but specialises in the luxury end of the market including land for redevelopment.
Give him a call and he will be able to point you in the direction of some great properties and also give you some good advice on how to handle the red-tape.
Good luck