Ironically, the 5R110 is already a 6 speed transmission. You just can't get access to all 6 of the gears.
It normally shifts from 1-2, 2-3, 3-5, and 5-6(od). If you are in 'cold weather mode' (5 degrees F or below) it will shift as follows : 1-2, 2-3, 3-4, and then 4-6(od).
If it could be re-programmed, it ought to be able to use all 6 gears. It doesn't give you an extra overdrive like the new 6R140 will, but it would give you the best of both worlds if you had 3.55 gears. You would still be able to pull a house through the lower gears even with the high rear end gears, and then when empty you would get the benefits of having 3.55 gears.
Now if we could get access to all 6 gears, and then also get something higher than 3.55:1 in our differentials, it would be like having 2 overdrive gears, kind of like the the new 6R140's.