[Varyon]

Were I the player, my inclination would be to have the ability perform better when I have a bow. So, let's say that with a bow and arrow the character deals 2d imp at Range 200/1000, and typically has Acc 3. I'd probably have the unarmed version be half damage, half range, and Acc 2*. This gets slightly complicated to build, but is easy to play. The easiest build is Alternate Abilities:

Innate Attack 2d burn (Increased Range x10 +30%; Increased 1/2D x2 +5%; Surge +10%; Requires Bow -10%) [13.5]
Innate Attack 1d burn (Increased Range x5 +20%; Increased 1/2D x2 +5%; Surge +10%; Inaccurate 1 -5%; Alternate Ability x1/5) [1.3]
-> Total [14.8], round up to [15]; if you instead round up each price first, total cost is [16]

An alternative build would use Either/Or Limitations and Limited Enhancements, and allow for a "Double Damage" Enhancement worth x2 to total end cost:

Innate Attack 1d burn (Increased Range x5 +20%; Increased 1/2D x2 +5%; Increased Range x2 (Requires Bow -10%) +9%; Surge +10%; Inaccurate 1 OR Requires Bow -0.5%; Double Damage (Requires Bow -10%) x1.8) [12.915], round up to [13].

In either case, the fact the better attack calls for a different skill can easily be called a Feature.

*The munchkin in me dislikes dropping to Acc 2, given it doesn't actually give any discount with either build (it's [-0.05] in each build). Indeed, there's a bit of a temptation to have Acc above 3 for the Bow version, thanks to the low cost ([+0.5] per +1 Acc in the first build, [+0.4] per +1 Acc in the second build). But, for the sake of flavor, I'd be willing to leave things as they are.