I have seen some where the BT has been removed, not sure what it does to the rigidity of the moke body but I don't think it would be
much of a reduction without it due to it's small size.
pic below of how the BT originally looked
and how it looks when repaired
replacing the whole floor is a big job and risky if you weld the new one in without holding the body square.
do you have any pics of the floor as it is?