You don't need to "dismiss the possibility" to say it's unlikely. There's really zero evidence this kind of research has been done a) at all in this lab b) on this Virus c) the virus leaked. Nor is it even clear the virus originated in Wuhan at all.
"Lab leak hypothesis" sometimes includes the "gain of function" theme and sometimes it doesn't. I find neither very likely, neither has any evidence to back it up. I still think the zoonotic hypothesis is the most likely truth, if not for the fact that we know this has happened so often in history. Any other hypothesis needs extraordinarily good evidence to convince me otherwise.
It does sound like you have a framework which may admit the possibility of lab-leak if specific evidence is found, in this case probably contemporaneous documentation of exactly that happening. I actually think we are largely in agreement then, I think though that it is very difficult to apply statistics here to gauge the likelihood of one or another event being true in the absence of much stronger evidence in certain directions. I'm only wedging my toes in the door of a not closed case, making no claim either way.
From my perspective there is a large weight on the case that the "lab leak hypothesis" is not true. To present it as equally likely is very misleading.
"Lab leak hypothesis" sometimes includes the "gain of function" theme and sometimes it doesn't. I find neither very likely, neither has any evidence to back it up. I still think the zoonotic hypothesis is the most likely truth, if not for the fact that we know this has happened so often in history. Any other hypothesis needs extraordinarily good evidence to convince me otherwise.