If you remove the diffusers you chance having a bulb fall out of its socket and down inside the panel.
I can suggest 2 options... either paint the inside of the gauge housing white or install a jumper on the headlight switch that bypasses the dimmer feature and provides bright as possible lighting. I do both rather than resort to white face gauges, LED bulbs, etc...
It may be just fine as it is now. Atleast your panel is easier to R&R than a rallye panel. Good luck