Well, I haven't seen your design, but they sound like reasonable requests - and it sounds like the Council is disposed towards approving the plans once modified. I don't think they have to give specific reasons for this, as they have not yet made a decision. But if it was me, I'd try to talk to the planner to get some sense of what the problems might be. Could be, for example, that your design is considered to be pastiche, and may not meet suggested good design guidelines. Many Councils publish such guidelines.