Wouldn't a weaponless person be at a disadvantage?
The only ones who would view it as unfair are novel readers, but will the actual character feel its unfair? Did Great Wheel Monk feel that way and did Qiu Qiaren feel that way?
IIRC Yang Guo was winning against Great Wheel Monk even while standing still and also beat Qia Qianren handily who Yideng could only hope to beat by a half stance.
If we go with the fact that the greats are fairly equal and Qia Qianren and Great Wheel Monk are also about Great Level, it isn't hard to see that Yang Guo would also be able to win against the other greats.
About giving the greats a weapon, I don't think Hong Qigong and Ouyang Feng improved their battle prowess even after using their weapons of choice during LOCH, I doubt it would matter if they use it against Yang Guo(assuming they're still alive).
Guo Jing's best art would be his dragon palms and his battle prowess would be worsened with a sword. That only leaves Huang Yaoshi.
It isn't sword vs fist that you see as unfair, what you see as unfair is how good the HIS is. Because as you see in the novel, almost every character would rather use their fists.
If he hadn't improved his internal energy that much, how could he last an internal energy battle with the Great Wheel Monk? He was nowhere near Great Level Internal to matching(but losing) in internal to a near Great Level.
That shows extreme improvement in the internal energy field.
But the argument really isn't about if Yang Guo can win against them, but their reaction and whether they will dismiss it, which I would say they wouldn't.