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Alpine Touring equipment is often a compromise between weight and function. I have some friends who use race boots and heavy equipment because that is what they have and can afford. The issue for them is climbing. Heavy boots, skis and bindings equals slow, plodding and strenuous climbs. Boots without a hinge at the ankle can make climbing painful and not fun. Wider skis (e.g. over 90 cm) force you to push more snow out of any existing tracks or generally out of the way when pushing in untracked new snow. Non-AT equipment can weigh as much as 12 pounds per foot, so you are correct in assuming that longer travel with your equipment would be hard.
The Shoguns are not a bad choice for what you have in mind, at about 9 pounds and 97mm under foot. Compare to what my Dynafit Manaslu's weigh (about 6.5 pounds).
With your boot, you will have to use a binding such as the Duke, Atomic Tracker, or the Fritche Freeride. I just got a pair of Trackers for slack-country, which is what your describing, and was impressed with solidness of the bindings and the ease of use for travel. Again, weight is an issue. The Trackers weigh 6.5 pounds, while my Dynafits weigh just over a pound.
Your boots also add weight. I think that the Langes weigh over 10 pounds per pair, while the Scarpa Maestrale that I use weighs 6.5 pounds per pair. If you want to stay with more of a DH boot, you should consider one of the newer boots that are designed for slack country (e.g. the Atomic Tracker boot). Still heavy, but good for both DH and shorter AT trips.
So to answer your questions. The Shoguns would work but have drawbacks. Consider using a Guardian or Tracker binding on the shoguns, that way you can still have a good binding for gravity assist skiing. Your Lange boot can also work, but is not the best option. Your whole set-up will be heavy and awkward (compared to AT gear), but do-able for short jaunts. On the other hand, my AT set-up , while light, will not provide quite the stability of the Shoguns and Lange boots on the downhill.
You still need skins, shovel, probe and transceiver.
I agree with Brian that sounds as if you also need experience, training and experienced people to ski with.