Give me a break, You can count on one hand the number of synth schematics that require scavenged metals. Synthweaving does not "REQUIRE" scavenging (and I believe they all use electrum).
If you count the faction-specific sets separately there are 22 different SETS of synthweaving schematics that use scavanged metals/compounds. At 5-7 armor pieces per set I'd hardly call that insignificant. The scavanged metals required for these sets include plasteel, lacquerous, laminoid, resinite, diatium, chanlon, polyplast, phobium and electrum. Did I miss any?
Great idea for the dye OP. Artifice can't use all the color crystals that are generated and they end up collecting dust or getting vendored - what a waste.