Inspired by the idea of a Martial arts tree, I tried to make up a concept how this might look like.
One prerequisite is, that Unarmed Attacks against enemies armed with melee weapons, get -20; furthermore Unarmed RoF is reduced to WS/2-1.
200 XP Talents:
> Street Fighting: +2 to attacks with knives
> Grappling: allows the grappling attack action (including inflicting fatigue, taking human shields or putting on manacles)
> Pugilist: adds + Strength/2 to unarmed damage
400 XP Talents:
> Unarmed Warrior: needs Strert fighting or Pugilist; RoF Unarmed becomes WS/2; attacks against armed opponents only -10
> Guardian: needs unarmed Warrior; may as 1 AP Reaction change position with an ally in up to 2m distance if he passes an Agility Test; the ally goes prone and the guardian is hit instead the guarded
> Wrestling: needs Grappling; +10 on Grappling attacks and all opposed test with grappling
> Sneak Attack: needs Street fighting; attacks against surprised targets with unarmed or knives get Vengeance (8) or their Vengeance improved by 2 steps if they already have it
600 XP Talents:
> Unarmed Master: needs unarmed warrior; no penalty against armed opponents; may parry unarmed; unarmed attacks gain Tearing
> Silent Killer: needs Sneak attack; improves Vengeance by 2 steps
Just a first concept though...