1) Most all brakes effect accuracty negatively to some degree. If you want accuracty don't get a brake. 20" barrels really don't recoil enough to warrent a brake. With #1 get the Phantom, not the AK brake.
2) I don't think BM flutes barrels onece they left the factory. However you could BUY a new barrel, or you could send your existing barrel to Kurt Wala of Kurt's Kustom for fluting (another forum on this board).
3) BM could install a 2 stage match trigger. If you want a better trigger you can swap for a variety of Match Triggers (single or two stage). Or you can do the 'trigger job' yourself (polish the trigger ping). Full instructions can be found in the "How To Do It" section at communities.msn.com/TheMarylandAR15ShootersSite
See our Parts FAQ for details on the different match triggers that are available.
4) WHY would you? DCM Barrels are meant for DCM competition and that is not legal.
5) Again see #4
6) None I've seen
7) Depends are the Les Baer (isn't that French for "I paid too much"??) designed to mate to mil-spec uppers?
8) There is no Mil-Spec for a cammo paint job on a rifle. Rifles are Mil-Spec when they are black. BM does sell a Camo rifle if you are intersted in that. Other wise you could get a cammo netting cover that are sold to 'camo' the rifles (they are currently being marketed to the military sniper groups, though I have not heard of any sales).