[larsdangly]

I am not eager to re-engineer the attack roll in TFT because almost anything you do will twist the balance of values of ST, DX and IQ scores, and as it stands that balance is pretty close to perfect. 'Balance with diversity' is pretty hard to engineer in a game, and once you tilt the balance the diversity tends to go out the window as well (because everyone understands there is a preferred 'build' to be had).

Nevertheless...

If I did go down this road, I would not do it by introducing a DX modifier you have to calculate all the time. Rather, I would simply use the contested roll mechanics that are already in the book (i.e., an attack is a contest of DX). If you enforced this across the board for all attacks you would increase the value of DX so much that you'd probably never see another PC again with DX below 14. But you just might be able to pull it off if you had a limited menu of options:
1. All out attack: you roll 2d instead of 3d for your attack, but don't get to contest any attack rolled vs. you.
2. Normal: you roll 3d for your attack and to contest other people's attacks.
3. Defend (a revision of the existing Defend rules): you don't get to attack, but
you roll 2d vs. DX when you are contesting other people's attacks against you.

I haven't gamed it out, but I suspect there would still be some sort of role for a strong brute under these sorts of rules.