Cofty, it's easy to put individual processes into words, then using connectives to put them all together. It's a completely different matter demonstrating the overlapping and/or merging of these processes in real life. I would be interested to see it demonstrated from A-Z.
So, one would have to start by demonstrating the spontaneous generation of living organisms from inanimate matter. From there one would have to demonstrate how these basic life forms, through what you call cell fusion, segregation and recombination, would be forming multi-celled organisms. Yes, endosymbiosis could be demonstrated in existing life forms, but how about demonstrating it all the way (from single cell to multiple celled organisms to complex life forms).
Now to show how these multi-celled organisms would create in themselves specialized functions in order for them to evolve into complex life forms. Complex life forms would then be adapting the processes of mitoses and meiosis, differentiating themselves into multiple sexes. And if scientists would succeed in such a feat, to put it all together and demonstrating it in a lab, they would be called gods, being able to create life.
I don't think the above would ever happen. Here I should add, finding basic life forms, or even the remains of life (i.e., fossils), on other planets, e.g., Mars, would help your cause no end. I predict they will find no life at all. So we will have to wait and see.