As for the brain, I would assume so. I'm surprised you can grasp with something embedded in your skull, and I haven't tried it out yet, but Putnam knows what he's talking about based on what I've seen. I wish there was a way to increase the range, but my experimentation in the arena with two grasping horns like a unicorn's seemed to indicate it's plenty useful at only melee range.
The chaos gland sounds like another good idea, using a similar system. I thought about giving them two magical graspers that way, which would make them a little more dangerous than unicorns in melee. Two chaos glands of sorts and a regular brain maybe.
I had planned on doing almost exactly that for the breath attacks. Based on reading the wiki, I suspect giving them actual breath attacks might cause oddities in combat, such as almost exclusively using the breath attack. But, I wanted them to have a wide range of magical afflictions, possibly coming from various types of draconequuses. One variety that does things like stun, paralyze or put to sleep. Another that sets fires. Another that causes localized tissue damage of some sort. Things like that.
Then I figured a true Discord scale draconequus might make a decent megabeast. More powerful magical attacks, more graspers, bigger, a magical shield, things like that.