"Mark- I'm beginning to agree with your last comment. I'd be doing "real" backpacking with full equipment while touring. Seeing that I'll be traveling solo at least part of the trip, my pack will probably be impossible to check in. "
Ah, ok then. It all depends on if you think you can get ALL your gear, both backpacking and traveling (perhaps you consider them the same) into < 46 l. Probably much less if you bring a (boxy) pack that has not been optimized for carry on. Even if you allow for squish, a "regular" pack is going to be less efficient. So leaving aside toughness for the moment you should be thinking ~ 40l volume total for everything for the trip not worn. Very doable, but depends on the level of flexibility you require for different types of activity.
If you feel you can do this then find a real bulletproof pack you can accept as a real backpacking pack. If not then there is the "classic" duffel method. Get a decently tough duffel that can be rolled up then you can store more or less whatever gear you would normally take on a backpacking trip, including the pack itself which can now be whatever, provided you pack everything in a way that protects it from the stress it is going to receive. Then when you get to your destination you can repack into you packpack, and roll upf the duffel and put it inside.
So I think the first thing to decide is between full-carry on and duffel method. The former is doable, but very much pushing it if you are bringing full, non-UL gear along. If the latter this simplifies things a lot. The main restriction then is if you can comfortably switch to "pack mode" with everything inside the pack. That is easy compared to trying how to get it all onto a carry on and having it be tough enough. There is also nothing preventing you from using a bulletproof pack AS the duffel, but you will provably get away with lighter total weight using the packable duffel method. You can also lock a duffel which is an added layer of security very useful for international travel.
From your description in the OP it seems like you are probably just over the edge into duffel territory.
@steven Yep, ripstop nylon is pretty strong. I would trust my golite jam under a lot of stress. However, I would humbly suggest that the "proper" test in this case is more like this - will both your pack, and everything in it, survive having a 200 pound box dropped on top of it?