[dsraven]

some of the trouble I have seen is also related to the weight of the shift levers and linkages and also worn out detents in the trans allowing the trans levers to slop a bit and the linkage to sag some which takes the "gate" out of alignment inside the box. the box can't hold the weight of mud on linkages etc. sounds like that wouldn't be an issue here anyway.
the neutralizer sounds like a great idea and is shaped so once you select the next gear range, or lever in the box, the other lever inside the box is held against the neutralizer so it can't sag out of alignment and it will always be a lined up "gate". it probably wouldn't be that hard to make one if you know a machinist or have a mill