One thing you may want to think about, if you're solely relying on an all-in-one system, would be something similar to the Eagle Industries Hybrid Sniper Rifle Case (HRSC). It's a drag bag, shooting mat, and backpack system all in one, where you could attach pouches to the outside of it for ammo/binos/tripod/etc. However Eagle stopped making them and their recent sale just offloaded the last of their inventory (I asked and they stated they have no plans of bringing it back into production). If you can find a used one, then it might be worth looking at. I know Galati makes their deluxe shooting mat bag that looks almost exactly like the HRSC, but I have never used their version. The built-in (full unzip) shooting mat is nice, especially if you're hiking out to a spot and its been raining or the terrain is talcum powder sand, that way you have a barrier between your kit and the elements.
Another option is going with something like an eberlestock LoDrag pack and using a scope/crown cover with the rifle placed stock first into the bag. I've used their GS2 for years now but have never run a 26" or folder in it. Just another thing to think about if you haven't yet. This would give you a platform that's actually designed to be used as a pack with hip straps. This may be more comfortable for you when hiking to your shooting spot.
The downside to the traditional drag bags (including the HRSC) is that they are massive and awkward to hike with when loaded down with kit. The are great for dragging to your FFP, but wearing them as a backpack is kind of eh.
Good luck man.