We combine the most efficient (chemical) approach toward three-dimensional photonic crystals with the most convenient (physical) technique for creating non-close-packed crystalline structures. Self-assembly of colloidal particles in artificial opals is followed by a carefully tuned plasma etching treatment. By covering the resulting top layer of more open structure with original dense opal, embedded defect layers and heterostructures can be conveniently designed for advanced photonic band gap and band edge engineering.