Unfortunately I don't have that kind of advanced tecnology machines . I have to find another way to check the solder jointsI second the idea for using some sort of hotplate. The PCB itself can bake at those temperatures for a while and worst case the soldermask might start to discolour. One of the benefits of using the hot plate is that all of your ground pours are completely at temperature and should only take a little bit of a kick with a heatgun to get over the solder melting temperature.
It might be worth to design some sort of chip alignment tool to make sure each of the balls mate with their correct pad. I've done some cowboy rework on smaller BGA grids and it was fairly easy to short out a single ball. You could do something like a PETG 3D print coated in foil or I've seen 3D printed jigs that use old PCBs as the bit that actually touches the chip since it'll resist the heat.
Unfortunate you don't happen to have an X-ray machine laying around to validate the solder job before power on
Thats what I wanted to do, since i have 6 PBCs avaliable, i can use some of them to practiseHe could make a board to train with BGA soldering before trying with the chip itself, in the worklog I talked about it.