With these things, you cannot deal in certainties. So the best answer is probably there is a high likelihood that a theoretical, voluntary transition like that would lower aggressiveness. However, and I assume the down votes are a reflection of that, there probably is a way to achieve that outcome, including medical procedures, that doesn't require a transition. And since that's unfortunately a hot button issue, linking a gender transition to a form of criminal punishment is not a good look.

Physical integrity is a highly valued right even in countries that still do capital punishment. So few people would put your theoretical plan here into a therapy plan or the law. A transition should be a personal decision based on an inherent need of the self and not an item on a menu of therapies that might get you out of the institution faster.

There are no stupid questions (well, hardly any) here but there are ones worded off the cuff that may lead to a pile on. I'm afraid yours here falls into the latter category.