Hmm. Here's my opinion.
The eberlestock's don't hold enough gear for real backcountry sheep hunting. If you add their super duffel or whatever it is the weight is way too far back. Their scabbard system works well for day hunts but like already posted you can't sit down for a quick break and when descending a steep hill I have to take it out so I don't hit the muzzle and then I can't really get the rifle back in with out taking the pack off because its loaded up.
I like to take a quick break with out taking the pack off because its kind of a pita to be taking a 60ish lb pack on and off and readjusting it to fit every time for a five minute breather.
Just like you, I can't get used to the kifaru system. It's just not right for me.
I run mystery ranch packs and put the rifle in the water bottle pocket like you do and I balance it out on the other side with water bottles and spotting scope. When I'm up on top of the hills and not concerned about bears I strap it in just like you have yours. Problem is, as you know it's not coming off without taking off the pack if you need it. I have tried to use accessory straps and buckle the top strap that secures the rifle to a point where I can un buckle it but it pulls too much on the shoulder straps when it's tight and makes the pack a little off balance and uncomfortable to wear. What I end up doing when I'm going through the timber on my way up and want the rifle available is putting it in the water bottle pocket with the shoulder sling around my head. It works but it pulls on your neck after a while. Or I just carry it.
If you're looking for opinions/suggestions I would love to see a pack that carries my rifle butt down not much lower than my waist belt, has 6500-7000 cubic inches of volume, is an internal frame( to keep weight down because ounces add up to lbs), is as tough as my mystery ranch packs and if possible a little lighter but not at the expense of quality and allows the rifle to be easily/quickly removed if needed. As well as being able to put it back in while wearing it. The deal breaker is being able to sit on a log, rock or stump without having to take it off or bump my rifle.
I don't think it's an easy task as I'm not aware of something with these qualities yet and I would tend to think that mystery ranch would of nailed it already if it was easy. I'm not trying to knock you or your company at all with that statement.
I hope you do try to make something like this and also that you join as a sponsor so Len doesn't remove all these posts especially since I actually typed it all by finger pecking :-)