To be honest, I would stay with the blue for the engine bay. A different colour engine bay than the body smacks of a respray on 1:1 vehicles. I good friend of mine had an originally black 1:1 R32 GT-R that had been resprayed in Japan (prior to importing into Australia) to a custom orange/red colour, and while the paintjob was first class, the engine bay remained the original black. It just wasn't right.
I say keep the professional look going with the engine bay the same colour as the body. You are bound to perhaps lose some of the detail anyway by the sheer fact that so many parts will be out of normal view (think of some of your suspension componentry for instance), but the devil is in the detail so to speak, and having a uniform colour within your engine bay adds to that detail I believe.
However, my opinion is but a humble one. I think whatever Hiroboy chooses to do, the final result will still be spectacular.