Thanks a lot for the help and suggestions guys.
I know its very stupid that our assignment doesn't have a certain criteria for operations. In other words its presumed we can use the aircraft for whatever we want. So with each modification I could perhaps tailor it to a specific type of operation. i.e. for ferrying freight in Africa and no night capability etc.
My bit in particular is to do with systems and avionics. Someone else is considering engines/ materials etc.
I think I have a much clearer picture now of what I can do depending on the operating environment however I still find the available formulas for DOC calculation quite confusing. I can't find anything simple and straight forward that I we can use to calculate DOC but I guess that's the nature of DOC.