Now, something I found interesting about Eunice is that in the first episode she appears in Azmuth claims that she is dangerous and can't be left to wander by herself. However he never explicitly stated what makes her dangerous. Which has made me think of a few possibilities.
The first is that since she is similar in function to the Omnitrix she also has the same energy as the Omnitrix. And as we have seen the Omnitrix is able to discharge massive amounts of energy. And if left charging for a few days it can destroy the entire universe. Perhaps this is the same for the Unitrix. The counter to this is that the Unitrix is less powerful than the Omnitrix.
The second is that she could be susceptible to viruses or hacking. And even species such as Galvanic Mechamorphs. And that, if hacked, could pose a great threat. The reason this isn't so bad with the Omnitrix is that the Omnitrix has less of a conscious to exploit. And is always carried around by Ben and is not wandering on its own.
My third idea is that maybe what he saw of her in the main series is actually only a small part of her ability set. Maybe she has the capability to not only borrow from different species but like the Omnitrix, she can completely manifest as that organism. Or even similar to Ultimate Ben she might actually have the power to borrow multiple DNA from multiple organisms but she just hasn't learned how to do it or unlocked that function.
But that's just my theory I wonder what other people think.