You must have had something majorly wrong or different from what we are talking then. Maybe you have some severly worn TRE's so they were essentially "rolling" beyond the original spec movement, a sloppy steering box, or "u-joints" in the steering shaft. All of the minor slop in these eventually add up to alot. I have also found on some larger XJ/MJ's that the frame deflects enough to show considerable amounts of steering play if the box is not braced. My YJ is about 9" lift SOA in the front (extreme drag link angle) and I don't get remotely even close to that much steering play. Also, the rusty's set up I have has tabs over the top of the tie rod the drag link attaches too so they are al in line and do not creat a torsional affect on the tie rod. Majo's jeep is only going to be 3.5" too so there would be a minimal drag link angle compared to what you have.
From when I first read your post it sounded you meant lock to lock because I consider a left turn or right turn to the stops. If you had had to begin to steer or something I would not have been mistaken, my bad.
I know my share of mechanical info, especially jeeps (built CJ2A's, CJ3B, willy's pickup, MJ, XJ's, YJ, CJ's, and working on collecting for my buggy). I have done high steer, corss over on a D44, over the knuckle on my MJ, and working on my D60 high steer arms with hydro to clear my hummer bead locks on the YJ so I have had some deallings with steering components. From what I have tried/experienced I feel that with his setup it should have no ill affects, only the positive ones and if he doesn't like it he can always slap his old set up back on (bleck...to inverted Y).