I have an Impact X in .22 and can reply to some of your questions.
As far as being fragile, if your going to put it in a backpack which will get bumped around and possible dropped a few times, my concern would be the scope, not the gun. Yes the barrel can be put on and off in less than a minute with no change in POI, but since the bottle stays on the gun you'd only save about 6 inches. If thats required, I'd say no problem. My barrel is 600mm, or about 24 inches. Most of that is very supported with the final 12 inches of barrel not supported and enclosed in a shroud with a 5 inch, very lightweight FX moderator attached to the shroud (it is VERY quiet). The barrel is stiff and you would probably dent the shroud before the barrel. I wouldn't worry about a few bumps into trees or whatever.
Shooting JSB 18.13 grain pellets at 860fps my gun is at 30 foot pounds. From a fill of 250 I get around 140 shots with the power wheel at max. My regulator is set at 110 bar. With a Hawke Airmax 4-12X40 scope and Burris Signature adjustable rings (I love the AMX etched glass reticle) it's right at 8 pounds. It is very accurate. This is how it came from the factory and is how I plan on leaving it. The gun is very easy to shoot offhand and does everything I want it to so I'll just leave it as is.
I can certainly see where if you wanted a bench rest gun to shoot at 100 yards or shooting larger game, increasing the regulator, adjusting the hammer spring, etc., etc., would be easy to do with this gun. If you get one I'm sure you will appreciate all the thought and engineering that went into this fine rifle.