DPoS suffers from a crucial problem which invalidates the whole system. There is no proof of stake, therefore there is no way to conclusively ascertain which chain is the longest and thus which spending is not a double spend. Meaning that DPoS does not prevent double spending.
I don't follow this reasoning at all. The shareholders are voting on the current transaction ledger. You can only change this by controlling how the majority of shareholders vote. You also have to manipulate the vast majority of delegates into participating.