Ah, but he'd already regenerated into the 10th Doctor before the hand was cut off. So I see no reason for Ecclestoneossity to occur.
Sure, I agree. However, RTD is not known for his strict logic and hard science. If Donna can become half-Timelord, I think Eccles can be the hand. Given everyone else is there, why not?
Hmm...I hadn't thought of that before. I can see what you're saying, but I don't think there's no way of ever telling for certain, short of Davies confessing.
Oh I agree, there's no way to really know for certain. But, watch the performance. The "Run" out of the TARDIS towards Davros, the manic grinning and 'rough' edges. Not to mention he's the one staying with Rose, and in my opinion Doc 9 loved her the most, and she needed him the most.
But, again, who knows...