Roger that on MOLLE all over the place. There have been a lot of great innovations that are MOLLE-compatible, without the webbing, but for these types of event-specific gear needs, I think custom is the way to go.
I really think it makes sense to approach it from what blasters, water systems, and other items you're carrying, then let that determine the design of the load-bearing system.
One of the most sensible rifle approaches I saw was the team that had the Proof Research carbon fiber wrapped barrel 6.5 Creedmoor. Also, If I were carrying a carbine for SAC, I would look into the AP Industries Carbon Fiber float tubes. I have a rifle-length one, and it weighs 5.6oz with hardware. I would also look into a carbon fiber wrapped barrel for both the carbine and the rifle, with a Ti muzzle break to help reduce muzzle climb.
I even noticed some teams that loaded the lightest weight projectiles possible in their pistols, to the extent of using aluminum cases to help with weight reduction. Pistols and mags should lean to the lighter models, rather than your full-size autos with steel frames.
Someone mentioned the Coleman civilian polymer frame that was adapted to ALICE packs by some sew joints back in the day. I have one of those frames, but I modified the frame to drop into an ALICE, rather than having the tabs with grommets sewn to the ALICE. The angled portions of the frame near your kidneys offer some unique options that would help keep a rifle as close to your C of G, without requiring a long sleeve.
I'm going to have to get my Coleman polymer frame out, but it's overseas right now. Maybe just get another one. I have a frame design that will integrate one common, but bulky, piece of equipment into the frame, knocking out 2 birds with one stone, and making establishment of positions much faster, without needing to break out ancillary gear.
I have to say that Tyr's innovation with low-weight Cordura and ballistic laminate coatings on the backside is one of the best things to come along since Cordura for military-grade textiles. What's wrong with decreasing weight, while increasing abrasion resistance and tensile strength?
