For a melee build you should keep strength, agility, and endurance at 7 minimum so you can access the best melee weapons and unarmed perks like unstoppable force or slayer. You could potentially start with a 6 in these stats and boost them using implants. Also, I think toughness and sub-dermal implant are important to any melee build, two ranks of toughness + the sub-dermal implant will provide +10 DT which is invaluable.