Setting the sniper up for 120 is as simple as a shock and fork.
I haven't had any of those issues. My bike is a large and fits two bottles easily in the front triangle. The 936 has one bottle mount. Sure, you need a wrench to replace the hangar. You need one for the 936 as well, but a small allen wrench rather than a larger open end wrench.
Sounds like you're simply wanting a change, so go for it. Mine is a T, so it has the extra brace on the rear triangle. Other than that the frames are identical from XC to T.
As for setup, I used the same components on both bike builds. Fork, wheels, drivetrain, cockpit, dropper, saddle.
Only thing different was the shock. Well, headset and bottom bracket too. I built the 936 with a fox DPS factory that I sent to Fox and had changed to 42.5 travel. I used a fox DPS performance elite on the sniper so I didn't have to see that annoying gold color. Functionally the exact same shock without the gold.
I built mine a couple years back, when the frame with shipping to my door was under $800.
At that price I might do it again. But really waiting for something else, and for prices to be back where they belong.
The sniper climbs and descends better. Noticeably. If you don't like whatever flex you are feeling with the sniper, I doubt you'll like the 936.
But get the frame. It's what you want to do, so go for it.