Your house rule to give +1 advantage (+10) is pretty close to the RAW, which would instead apply a penalty of -10 to the Brawler instead of an advantage to the weapon holder.
Have a read of Weapon Reach and In-Fighting on p.297, and then In-Fighting talent on p.139. I recommend you use the optional rules for In-Fighting.
Basic summary: the core rules do not differentiate melee weapon sizes, which means the person with the melee weapon uses their Melee (basic, or whatever) skill and can use it's traits (if any) and likely will inflict higher damage on average (SB+4) that the person using their Melee (Brawling) skill using their fists (SB). However the core rules do give an option to use weapon lengths and some talents which influence this style of melee.
If the Melee(Brawl) person has the In-Fighting talent they do not suffer a penalty to strike the weapon wielder. Further if the In-Fighting rules are used they gain a +10 bonus to strike the armed foes.
If you use the In-Fighting rules option, the person using Brawl to attack a weapon holder suffers a -10 penalty to hit. They may also choose to forgo damage, and instead use a successful "attack" to instead step inside the weapon holder's guard, and fight closely. If so, any weapon longer than Short is improvised (meaning SB+3 and no specials traits instead of its normal qualities)
Hope this helps,