I actually think this is the best skill system on PES for years. It reminds me a lot of Fifa 98's skills which were fantastic
The rainbow flick is a bit too easy while using good players, but have you tried using your BAL player to do one - not so easy. I'll also point out I cant play football to save my life but I can do a overhead flick with the best of them - despite apperances an overhead flick/rainbow flick is actually one of the easiest skills in the world to pull of.
Think link system is dificult if you just use the 'heavy hitting' skills like Elastico, Rainbow Flick and Inside Bounce as they all take the balls in different directions and this gives the oposition more chance to get the ball. But if you link step overs and drag backs and add a heavy hitter at the end of a link, you'll have a much better chance of pulling them off.