I think webbing/ALICE might be a good option, and I prefer pistols. DROP THE SPOTTING SCOPE, you'll NEVER need it, try a set of 10x25 binoculars, they'll serve you much better. A friend of mine built a sniper's rig with a ghillie suit, and a MOLLE bandoleer, it was built for a M16 SPR/DMR with an ACOQ 4x32 (closest thing to a sniper rifle in my group). Drop the scabbard, keep the rifle on you (3-point sling), and get a holster for a pistol (think of getting a pistol lanyard for it too). Do you already have the rifle or is this an idea in the making?
SRC HK416(D10.5) gen.3 pro
KJW MEU(SOC) pistol (cansoft)