Can I admit I'm a little disappointed? I was picturing the Bigfoot Monster Truck of skoolies! LOL
Okay, now that we know what animal we're dealing with... Yes there's going to be some shift in CoG - but - this seems a bit more manageable. More imperative than weight alone is the lateral forces at work when the bus goes off level surfaces or also expect more fight from crosswinds when you're rolling down the road. As I see it, you've increased headroom but most of what you'll install is still going to be low, and that's even assuming you build up the floor a foot or so. Heavy stuff like water tanks and gensets and batteries usually go at or below floor level so these will add weight down low that helps combat the negative effects of the tall wind sail of a side. If there's still some body roll following the build, two things to do - add more leaf springs (unlikely but possibly) and add/increase the sway bar (also called a stabilizer bar) capacity. Adding leafs to the suspension increases the load capacity but if this is required then you probably have an overweight issue anyways and while adding capacity here helps it doesn't address all the other weight bearing components which are equally overtaxed. Fortunately most buses have much more overhead weight capacity and I am less likely to expect this to be an issue you face. Alternately, adding a sway bar or swapping out the original sway bar for a beefier one is exactly what addresses the side-to-side sway of tall or top-heavy rigs as well as combats crosswind sway. When one side bears down on the sway bar it translates that force back to the side that's on it's way up and vice versa so body roll is reduced. It doesn't increase weight carrying capacity or change the ride characteristic beyond that function described above. This is actually a common upgrade for RV owners because sometimes the OEM sway bar from the chassis manufacturer wasn't big enough to handle the rocking of a tall RV body. Of course any RV upfitter worth their salt should probably know this and already order a better chassis or swap in a bigger sway bar as part of the prep. Since this is essentially what you're doing is adding more body height than what the manufacturer originally spec'd I think this is going to be an easy and effective resolution.
Keep us updated on your build.