General Discussion

It will cost hundreds of millions to upgrade the thing to AF1 specs (likely more than the $400 mil the plane itself is supposedly worth).

Why not save even more and just keep the current AF1s until the new planes are available??

Of course, the obvious answer is that Trump wants his own gold plated air-bordello and he wants it now. I expect the sequence of events will be he accepts the g(r)ift and when the exorbitant conversion costs become better known he will simply "donate" it to his "library" or some other entity controlled by the Trump Org and use it thereafter for personal purposes.