i'd rather not have nightvision be something that requires cost and space. Mechwarrior 4's 1 ton mech sized NV goggles was just silly, especially considering all the sensors already mounted on bt units
just one thing though, please for the love of god, whatever route you go with nightvision, please, please don't do the horizontal lines that crysis has it its nv. you can hardly see anything at range with those things ruining any definition. Those horizontal lines are not even present in present gen nightvion anymore, and even less likely in the 31st century.
as for floodlights, they'd probably be more handy in spotting elementals since nightvision doesn't create any shadows and offers less contrast than something brightly lit. also great for light blinding people at close range