I had similar questions that I put to lawyers and other foreigners who had done similar things. The answers I got (which were all different as will be all the answers on this thread) can be summarized:
The lease is only as good as the person you lease it from as they can sell the property and then its up to you to convince the new owners to honor the lease (which could get expensive for you).
Its best to get a 25 year lease that you can opt to renew for a further 25 years at a set amount and its best to pay the entire 25 years in advance and get the lease and receipt notarized.
The plan is to die before the lease expires and then the property owner gets the property and all improvements but I have not heard any reason why you cannot sell or remove any of the improvements unless the lease specifies otherwise.
I have seen no guarantees that stop a foreigner from getting screwed over so I re-emphasize my first point about being sure you are leasing from a reputable person or business. Let the buyer/lessor beware.