If the build is designed as a PDW, with the parts you have shown I would use the following :
-553 with the Matech irons behind
-magpul grip
-Stubby vertical grip or AFG, whichever you prefer
-Surefire Scout
-keep the current stock, CAA is low quality.
Some upgrades I'd suggest:
1. A light mount that offsets the scout, like the S&S or Gear sector one. I think I mine is S&S but I can't seem to find it on their website. This will allow you to get a high grip on either your VFG & tube or the AFG and actuate the tailcap with your thumb. I don't know if you can move the rails around on that tube you have, but with an offset mount you can mount the light on either the 9 or 12 o'clock rail for a right handed shooter.
2. Every rifle needs a sling. VCAS or Vicking tactics slings are great for most applications, however if you are using the weapon in a vehicle then a single point wrapped up with a rubber band is less prone to snagging.
3. A front sight. Whatever you prefer but I like a fixed LMT iron sight.
cheers