Thanks all for your opinions.
It's hard to bring the whole team for discussion. My team performs unexpectedly well in this season with 6 points leads in a league with opponents with similar qualities. It also leads the league in scoring. But it is strange that there is no outstanding scorer in this team.
Among my 4 strikers, there are 1, 1 and 2 using either, left and right foot respectively. My most trusted striker is low 5 star and use both feet. But most of his match ratings are just 7. He also seems not good at free kicks. The striker with best rating is higher than 4 star and right foot. His average ratings is close to 8 but he has more assists than goals in this season. I think I will use this player more from now on and try to use him as free kicker.
I have not yet identified the most reliable free kicker in this season. That's why I am still considering those FK specialists. My FK specialists are either slow or average trainers. If they cannot break into the list of FK specialist, they will unlikely break into it in subsequent seasons.
The first player "Die" was a pretty good free kicker two season ago. So I used him on this and assigned him some attacking skills up to a point that all 3 types of attributes are close. In last season, he gradually lowered down in the list of my free kickers and I assign him defensive skills. Now in season 3, as 4 star player, he become my best pure defender.
I think that even if the FK specialist is a defender, he should give a chance to try. If he's good, I will assign some attracting skills to support him. I am never sure how to manipulate skill development to shape the player into a good one.
In general, I usually avoid to involve in bidding wars for players with SA. So I don't choose positions for FK specialists. All my players with SA are acquired with at most 3 tokens.