So I have a new doubt concerning wound allocation.

Les´s suppose my unit "The Boss" is hiding behind a wall, away from all enemy eyes, exept for say, the medic, who can be seen by the enemy. Now lets suppose an enemy unit shoots to The Boss because they see the medic. And lets suppose they make 2 wounds (after cover/armor saves). Since they see only one miniature its clear, by the manual, that they can only hit one miniature.

Thing is, can I assign the damage not to the medic, but to the mechanic or any other miniature instead?

No, third bullet Step 5 page 44.

Thanks a lot Tanker! Youre right, I must´ve misread it, because its pretty clear. Thanks a bunch man!