No one here has mentioned malachite. Ya know, that dark blue stone. Of course, turquoise is lighter blue and may match the flag color better. Semi precious stones used to be really popular for spacers. I like the blued blade idea, but think it would have more effect if you could really keep it a blue color, and be careful not to go too far so that it's black. Perhaps fire blueing? (depending on steel type- don't want to temper it too much) Or even make the fittings from mild steel and fire blue them.
Also, I really think you could take that 5/7 idea and run with it. Make it the whole theme of the knife. Make the blade 5/7 inches wide, for example. (or I guess they use the metric system there. Maybe 5 cm wide? Are there any ancient measuring systems that could be used?) Even the curve of the blade itself could be some mathmatical percentage involving 5 and 7. Maybe some file work involving 5 or 7 in a repeating pattern. Would you feel comfortable ginding narrow multi fullers? Like, say, maybe five of them down the blade? What if you put five of something on one side of the blade, but not the other? It would 'cry out' to the other side of the blade to make it complete. Or even five notches in the spine crying out for 5 serrations at the edge? Just thinking aloud here. The possibilities are endless.
Whatever you do, don't start grinding yet. You need to spend a month attaching symbolism to every aspect of every part, or after it's finished, a brilliant idea will hit you once it's too late to change.