I have an MWS and CQB. The CQB is everything the MWS is not, light, fast pointing, and agile. I use athletic terms because the MWS is just such a big lumbering beast that picking up the CQB is like dropping the weighted on deck bat and picking up your working bat.
Avoid the urge to add so much stuff on it that you take away from that lightness. I have a set of top rail KAC 200-600 on mine. There is a USO 1-8X on order with an ADM mount standing by for its delivery. The KACs are great and they come up in the gear for sale section quite often. I've bought a few sets BNIB for $225-$250.
I have a set of KAC 45 offset BUIS on my MWS and they are pretty fun to mess with. I have a second set that I will probably put on my CQB when the scope comes. Once the scope is on Ill never use the QD feature, save for maintenance, and I think I will play with the ability to roll the rifle over and use the KAC offsets to knock steel or some target innapropriate for the scope setting.
I currently have the bipod from my MWS mounted on the CQB to do some load testing but I dislike the weight. This rifle is fun for shooting from what you have available. Less is better. I bought a light for it but its never attached only available if I ever need one.
Choose what you want for Buis but what you do need to buy is
1. Extra barrel bolts from LMT at $10 a piece. Keep a few as spares.
2. A good tourque wrench as the one supplied has been known to snap item number one.