Ive thought about this myself, I think it would look rather nice.. But as i understand, its not just a case of cutting the roof off and fitting a fold away hood.. a lot of the body strength in a convertible is carried in the sills.. So id imagine they would need to be strenghtened in some way.. The mrs. has a convertible astra and that has a lot of support in the windscreen frame and in the rear head rests incase of a roll over... I wouldnt imagine it been an easy job, and the costs would far out weigh the cost of the car in the 1st place.. But I have to agree it would look verrrrryyyy nice...
Good luck...