I just finished adding the Wall SA to my 18yo DL/DC. he ended up being my lowest rated player over the course of the season as all his skill points went to his SA instead of his abilities, but I figured he was a fairly fast trainer and would catch up over the next few seasons until I sell him, but he got injured the training session right after I assigned the last skill point to give him the WALL. un-****ing-believable.
So I just bought a new 18yo, worth $2M more than my injured guy, so he should be a faster trainer, which is good, and here I go AGAIN. He was also 39Q instead of 34Q like my old one, so an upgrade in every way.
But yes, it is good to give an SA. But realize that 50 skill points is 2/3 of a STAR. My 39Q DL/CD can be 42Q but without the Wall or Aerial SA, he is not as attractive to me. I would rather have a 39Q DL/DC with WALL/AERIAL instead of a 42Q DL/DC.
That being said, I would rather have a 39Q ST with freekick or 1v1 instead of a 42Q ST with nothing.
Get what I am saying? It all depends on how fast you can get him the 50 skill points. If you powertrain, then it takes 2 days or so, possibly one if he is a mega fast trainer. Someone will correct me with the proper time period of course, since I only read about this.
ST: freekick or 1v1
AMC/AMR/AML: Shadow striker
MC: freekick or corner
DMC: playmaker
DC: Aerial or Wall
Those are what I would strive for.