Oh Jeffrey, you should know better than to ask people for their opinions.
Especially in this context.
But here's mine: Aluminum plate could make a great floor, but substituting
a new material for the plywood will open a can of worms you may prefer not
to deal with. Leaving aside the weight question, you have issues of
thickness of material, galvanic corrosion where aluminum meets steel,
fasteners, relative strenght of aluminum vs. pywood ....A potentially much
longer list. Much of it has to do with how the AS was assembled, and how
parts depend on one another structurally.
Sort through your intentions, then see if the exercise will meet them.
Louis Joyner