i wouldn't bother with a FLC since you won't be in a situation where you'll want to drop the MOLLE attachments on your flak but still need the flak. if that's an issue, just use a MOLLE war belt and attach your mag pouches, drop pouch, and IFAK (if you want to be authentic) to that and have nothing on your flak except a CAT tourniquet. that's what some of our guys do, and something i'm thinking of doing if i don't get a HSGI Weesatch before deployment.
as for slings, i would highly recommend either a one-point or improvised one-point using 550 cord. 3-points are irritating to no end.
bellevilles are awesome. i'm still rolling with mine from boot camp and they've outlasted two pairs of bates combats which were awful, straight awful.
as an interesting note, instead of flight gloves, a LOT of marines in my battalion roll with Blackhawk SOLAG nomex gloves with padded knuckles, especially some of our SAW gunners. i personally use a plain set of mechanix mpact gloves, but am thinking of switching out to something else with better grip.
i would HIGHLY recommend a set of kneepads, and alta makes a superb set. i'm relying on a set of hatch ones i got out on town, and really only needed one out in the field for my dominant knee since i would take a knee a lot and had the weight of my fully loaded ILBE and AN/PRC-117F in it.