Didn't think things through. This Alister was more than just emotionally invested wasn't he? It was through him that 'Lombax' tragedy had unfolded in the first place, whatever it may be. Though it wasn't as though this was as pressing a matter as Alister clearly was if these memories were on the forefront of his mind. His mentor, ally, fellow lombax? And he killed the boy.

Alister was an interesting character indeed, but what was more interesting were the feelings of isolation that he picked up coming from both of them, Ratchet considerably more so. Cut off from his entire species, friends and family. That was something to consider, now wasn't it? He also made a mental note of those wrenches, knowing that if those were powerful weapons and tools he possibly had access to other devices just like it.

All and all, Ratchet was the hero type. Incorruptible safe for Harth's one little trick up his sleeve and no guarantee that would work.

He focused on Ratchet's memories of Alister and some of their interstellar arena's. Let's see how Ratchet's current mind set deals with Alister? Face him as an enemy or not?

And he would take the role, as far as Ratchet knew, he was Alister.