I believe the Expedition version does what an extra buckle would do to a 2-buckle boot. It really molds the whole boot construction with your lower leg and increases support in all directions - without impeding walking. Kind of like Jaure. I've seen the way you describe Guide BC as bottom heavy, and while I believe it, I dont really see this in the Guide Expedition. As such, I think the expedition version is indeed more balanced.
If you have the Jaure, I guess you understand what I'm describing I use Jaure II LT and Forest II (high shaft), as well as Park (low shaft), and only the first two are mountain grade in my opinion.
I haven't tried the Alaskas, but I do certainly think the Lundhags Expedition would be more supportive. Maybe not the regulars BCs/Abisku. For example, I'm now using them with switchback and 86mm wide skis for resort skiing. From what I'm hearing, that wouldn't be recommended with Alaskas. In terms of support, they would be akin to the Transnordic but without the German's preference for torture.
For the use you describe on the Ingstad class, I wouldn't think twice about going for Expedition this time around at the cost of +100g! Just keep in mind that they are slightly more voluminous, so you may need a thicker sock to sit tight.