To inject comments like, "Let's assume that the LA is good and ethical" is doing EXACTLY the opposite. Anyone makings such suggestions should most certainly be avoided! To make such comment with no effort to gather additional information is reckless.
In some cases, the final negotiated purchase price will be what determines if the home will be a short sale or not. Should the owner perceive you are going to continuously negotiate the price lower, pushing it into a short sale situation, your offer can and should be rejected by the owner. The listing agent is not the decision maker but can provide guidance to the seller regarding what a typical buyer will do.
If you have packed your offer with contingencies, especially, appraisal, there are real issues that must be dealt with that will take time, effort and most likely result in a failed transaction.
Finally, should you prevail and the seller accept your lower offer, triggering the short sale process, the banks involved may come back with and even higher counter. If it is perceived you will cancel your offer at that time, then there is little point in accepting your offer in the beginning, if the perception is you will walk resulting an yet another failed short sale transaction.
In the 'Wild, Wild, West' of real estate known as short sales you really need an experienced guide. The illusion of rules lead many to believe what is vapors to be the law of the land. Every situation is different. Without a great deal more information, one can only make misguided statements.
In a short sale anything can happen. What MUST happen, in a typical short sale, is the buyer must demonstrate a commitment to see the process through to the end. Without this, everyone is wasting valuable, irreplaceable time.