Going back to the "one man's modus ponens is another man's modus tollens" principle, what you have to realize is that, given two contradictories, a person will hold to one of them based on how convincing it is in relation to the other one. Therefore, even if one can present a pristine, unassailable argument for Christianity (which is a lot tougher than "where'd the laws of logic come from?", by the way), it can only help to engage in polemics.
But, given the fact that we always fall short of philosophical certainty, so long as we are not omniscient, there is no such thing as an "unassailable" argument for Christianity, not in the sense that no more warrant can be provided for it.
Which is one of the many defficiencies in the evidentialist approach to apologetics. I measure the worth of an apologetic approach by its efficacy, not its difficulty. As has been pointed out though, Bahnsen, a presuppositionalist, was well versed in philosophy and I surmise could navigate his way through an evidentialist approach. Employing pressupositionalism though eliminated the need.
Regarding your above assertion that presenting a pristine argument for one's position will only serve to engage in polemics, as the other person needs to be dissuaded from their position before accepting yours, you again highlight a defficiency of the evidentialist approach. My assertion regarding dysjunction holds true logically and that's all I ever asserted it did. If people were logical, rational, and persuaded by reason, not by the work of the Spirit, then there would be no atheists. The Bible itself explains in very brief detail that no one has a reason to deny God's existence because things exist. That is enough. Secular science has spent the last 150 years trying to find an alternative explaination for existence so as to defeat this very simple fact. Why are there atheists though if its so logically apparent? Because men's hearts and minds are darkened. They will deny the light of day because they hate it, no matter how apparent it may be. This fact bears no relation to simple fact that, logically speaking, if it is true that theism is true, then atheism is, by logical function, false. The assertion that to engage in this sort of argument is to engage in polemics only highlights the problems in the evidentialist approach.
And, to be honest, I find it a bit surprising that in response to the OP, you're actually saying that apologists need to do less work than they're presently doing.
Well, for one, I disgaree with the OP. For two, I certainly have the right to an opinion, as suprising as you may find it.