Why would the big holders want to attack one of the chains?  Their holdings are in both chains, and they can keep, move and sell them independently.   Whatever value each branch of the coin has, attacking one branch will kill its value -- which will hurt the holders more than anyone else -- but is unlikely to raise the value of the other branch by the same amount.  

The holders should *pray* for a proposed hard fork will EITHER fail quickly to gather any support, OR quickly achieve majority support and end with a clean non-eventful hard fork.  Any fork attempt that does not resolve cleanly in one of these two ways can only harm the value of their holdings.

If the worst happens, and there is a disputed fork attempt that ends with a coin split (which, in a hard fork with 75% trigger, is VERY unlikely to happen), the best strategy for holders is to keep quiet and wait for the market to define the values of the two branches.  If one of them is quickly dropping to zero, they should dump what they can of it, and then just use the other -- in which case the situation will be the same as after a clean successful fork or clean failed fork, only with bombed buildings all over the place.  If, by some miracle, both branches retain some value, and they seem fairly stable, the holders should keep and use both, or SLOWLY sell the one they don't like to buy more of the other.