Shader hack ?

[NaN]

Nan can u assign the car body shader to the glass and have the transparency be set by a value in "car".car data file

Example

[glass]
texture = glass.png, glass-misc1.png
mesh = glass.joe
alpha = 10 (where 100 is fully transparent)

I think setting color should do the job (need to check though):

[glass]
texture = glass.png, glass-misc1.png
mesh = glass.joe
color = 1, 1, 1, 0.5 #rgba, a=1 opaque, a=0 fully transparent

glass.png is multiplyied by this color, allowing you to increase transparency of glass.png