Double07even - From my perspective, adding new special gadgets or chips that can be used on the character if they are found, crafted during the journey, or purchased from vendors would be enough, although from what I've seen there are already some character upgrade mechanisms, hmm, or if so, adding a new type of character prototype to choose from with its own unique traits, I don't know if developing passive character skills wouldn't break other game mechanics.
The white ones are called milkies, they and the experiments both originate from orsoniks previous games, not sure how far back milkies go but they were from gunsaw to my knowledge. There are plenty of other species in gunsaw that could potentially be brought over to casualties unknown, though I am unsure on the timeframe of all this, cause gunsaw is a decent chunk in the future compared to casualties unknown, plus experiments are described to be the first species brought in large numbers to the planet on which both games take place. Maybe a couple more species could be possible cantitades for addition into casualties unknown, idunno really.
On milkies themselves though, they are described as dextrous but frail specimens, with incredible intelligence and they tend to speak in a formal manner, though I havent actually managed to notice the difference between milkie and experiment communication.
Experiments have also been described as being basic, a template for all the other species, there isnt much special about experiments.