Birkin really only had control over himself in the early stages of his transformation... which goes along with what I initially said, about how long the individual is infected, being part of the how much they can control it. The later stages don’t allow for this with Birkin or any other tyrant that we have seen.
Lisa Trevor, on the other hand, is a different case all together. She is not like any of the other monsters/tyrants. What I always found tragic about Lisa’s infection was how it seemed her mind became stuck on her final thoughts before completely transforming. She sounds like she is crying as she roams around and occasionally moans “mother”.
Unlike the other virus strands, her infection gives her some form of memory to the point where you sort of wonder if Jill or Chris could have reasoned with her to some extent. When we first see her in the cabin, she strangely only knocks out Chris/ Jill and even moves them closer to the fire before they come to. I realize that reasoning with her might be a stretch but she also didn’t seem like a full blown monster ready to eat and rip apart everyone either.
The final fight, in the catacomb, is where we see Lisa finally getting what she always wanted. Her mom. She is completely distracted by the remains of her mom and loses interest in Chris and Wesker.
Going back to Steve. I guess I can see how someone might see it as a cheesy love moment when he transforms back into a more human form. But I personally never had an issue with it as he still appears somewhat infected (in the Wii-make), it is a different type of virus, and it’s truly a nice way to allow Claire and Steve to say goodbye. His body is in limbo as he is dying and both the virus and Steve are weak from the fatal wounds.
I really wish they would remake CVX. In part to make the story of CVX more fun to play through (it is such a long game with a lot of back and forth running around) and to also modernize the story a bit more and make it more dark, like the other remakes, with some good graphics.