In one of the companions(IV? V? VI? Arms Comp?), a great TWC rule we used was adding the Fumble range of a weapon combo together, and every rank developed in “TWC X/Y” allowed one to use a % of the OB from their already developed weapons.
So, two Maces with Fumble ranges of 1-2(x2) = 4.
For every rank in “TWC Mace/Mace” earned, one could use another 25% of their total OB with their Mace skill.
(-20 to LH use notwithstanding, of course).
It allowed more Dev Pts. to be retained due to not needing to develop actual handedness.
PS: for skill cost, I believe it was add both skill costs together, so:
3/7 Mace + 3/7 Mace would be 6/14 for development cost of TWC, slowing development down to 1 rank / lvl in most cases.
(That was where another optional rule was used in my campaigns - rapid development costs would merely be spending enough Dev Pts. to afford the second number of a skill’s cost, vs adding the, together like normal.)