Before you get too far down the track, see if you can get a hold of the AMI (Aircraft Modeller International) for March.
There is an article in that on "ribless D-box construction". Now while this has been written for my speciality (F1A glider), it should not be difficult to adapt to the kind of model you are thinking of.
I haven't read it yet - just returned home with it from LHS
- but the principles have been around for a while, and it is simply a matter of double skinning uni-d cf under woven cf.
There has been mention in recent times of "co-weave cf and kevlar". I first saw this about 15 years back, in 6oz upward form, too heavy, no dang good for models. That product seemed to disappear - it was horrendously expensive as well. At the past Worlds the Chinese turned up with d-boxes on F1A and F1c models made from a similar product. So keeping an eye out in some of the specialty places on the web might be an idea as well.
With good design. you could prove the combat nay-sayers completely wrong... good luck.