I converted to a single rear axle with a forward liftable axle two years ago and I love it. My advice would be to leave your rear axle and remove the forward drive axle and replace with a liftable axle. It cost a little more to do it this way, however this is the better option. You need to have an equalizing valve installed that keeps equal pressure between your drive axle and your lift axle. I use a Williams equalizing valve. Some people do not install this valve and just have a constant setting on their lift axle. With a constant pressure setting the lift axle will at times actually pick up much more weight than the drive axle which leads to spinning out or loss of traction. The equalizing valve adjusts momentarily on the fly so your weight distribution is always equal at all times.
I run northeast, tankers and van trailer. With tankers I'm 80,000 one way and empty the other. With van trailer I'm around 75,000 almost all the time. I converted to super singles, (Michelin XDA energy for the drive axle and Michelin XTA for the lift axle) and on my first set I got 110,000 out of the drives and it looks like I'm going to get just over 300,000 out of the lift axle if the wear stays true. I drive on snow and ice quite a bit and really don't have much trouble. Sometimes if I get into deep snow, like in a parking lot, I will spin out or loose traction and I usually just hit the button for the lift axle and that drops all the weight on the drive. Usually that will get you going enough to start moving again then I return the lift axle to the downward position. I don't have a full locker in my rear axle and I've got along without it for the last two winters. If you can install a full locker I would recommend it, you will double your traction in a slippery situation. I believe that a good conversion, (meaning rear drive axle with full locker, forward liftable axle, and equalizing valve) is actually a much better setup than duel axle with power divider. Hope this helps.
Yes, I've heard of that. On our conversions the only way to adjust weight is on the valve itself, which is located outside the cab between the frame rails, usually mounted on a cross member. There is a screw on the bottom that can be turned in or out to adjust weight difference between the two axles. Although it may be better to have more weight on the drive, I agree that probably your best bet is to keep it equal.