I don't doubt you, but I've come to very different conclusions about the effectiveness of the game. I'm wondering where my disconnect comes in. I think the main thing is that there's zero work put into pre-establishing the character (because obviously he's a surprise twist at the end wah-hey) so I don't buy any of his actual actions as character. There's no hints of two warring personalities inside this guy, there's no ideas about 'oh yes this is the medic character and the boss imprint clashing, here's where X shows through, here's where Y". It's just a series of actions a guy takes for reasons that are inscrutable.
Moreover, his character doesn't mean anything. It doesn't pay-off, mainly because last second reveal so there's no room in the actual story to do anything, and that it doesn't really make anything in the main story make any more sense or reveal more meaning or anything. It's like, Venom's just this guy, you know?
You can get more interesting stuff by theorycrafting about MG1 and 2 or whatever but it doesn't lead anywhere except epileptic trees and fanon.