Well, my biggest issue with the arms is a thing that Bionicle has done for the longest time, and that I myself do quite often. But when I can, I attempt to give MOCs lateral bicep movement. Most all my Toa Team outside Baronon has it
If you look at a MOC like Nyran, for example, you notice that the upper arm is like an HF Bone. Ending in a full balljoint, but starting in a socket. By using that balljoint as the end of the upper arm, and then using a socket joint as the start of the lower arm, you're able to get movement up and down, like normal limbs, but you're also able to move the lower arms across the body, or outward, should you want to. Like, he could cross his arms, or whatever.
So, what I recommend, for the upper arm, is to take out the hand piece there, and replace it with a Glatorian neck, or a Hordika inner head piece. And for the lower arms, I'm not exactly sure. How many half-pin deep lift arms do you have? Y'know like this or this?