Note that lightmap.cpp:144 is not meant as a permanent modifier. (And should have been commented with // FIXME or // TEMPORARY - reason why). Any change to veh_type would also be temporary.

The power will likely need adjusting once apply_light_arc is corrected; it's currently hard coded to 90 degrees and spits out a beam that's too wide and too short even before the truncation issue is taken into account. During the course of correcting / redoing apply_light_arc, before a commit, headlight power will be changed multiple times for testing, and it might need further adjustment based on user feedback etc.

And if it's defined in veh_type.h, this will force a rebuild of virtually the entire game.

Hopefully this makes sense. Anyway, I'll adjust, and assuming I do poke at apply_light_arc I'll fudge the arguments or something for testing.