I was thinking of changing the generals science system... Instead of u gain xp and levels to unlock the sciences you want... I was thinking when you reach an higher star or rank, you automatically unlock all sciences of that rank... and starting with no rank and no sciences... Is it Possible? Or it will be too much buggy?

Try Editing the Rank INI and find the Science Points Purchase Granted. Set your own Value

Nope That will only give you more Gen points. What you actually have to do is

for each rank.