Ordering a blond 0,03mm v-lopped unit would it be possible to dye it darker? Any theoretical suggestions to this innovative approach giving a even more natural look as the hairs between the layers of skin would be blond.

Jorn,
Yes, you can dye it darker. Use the normal dyes but don't allow the dye to run down on to the base. Some people pin the unit to a styrofoam head. Put some newspaper down on the table to catch the excess runoff. The turn the head upside down so that the hair is flowing downward. Put the dye on a comb and comb downward. Or you can just put a little bit of dye on the comb at a time and comb the dye through the hair being extra careful not to allow the dye to run down on to the base. You want to keep the dye off the base and get only the hairs. It's a little tricky---please take your time.
Good luck,
John