Just to point out, the bumps and lumps on Eldar vehicles and armour were never meant to be gems. They were supposed to be aesthetically-pleasing curved shapes to cover what would be unsightly sticky-out bits (joints, hydraulics, etc.) or access panels on non-Eldar vehicles. The only ones that were supposed to be gems were the ones mounted in specific mountings, like the main chest one on Guardian armour, etc.
The reason they got painted as gems was because of a mistake by the 'eavy Metal team, which has made life hell for Eldar painters ever since.
Sorry about that...
But it does give you an out, eh?

(The paint job's looking really good, by the way. Love that deep red.)