Sad to see Planes go but I was kind of expecting this to already happen when Laporta took over. He did some good job so thanks for everything and good luck to him wherever he'll go.
Between three most serious options to replace him (I doubt we'll go for an "outsider" like Rangnick) Overmars is the best choice imo. Love Puyol but he doesn't have much experience as a SD. Jordi did a good job building teams in Cyprus and Israel but Barca is a different beast.
The negative side of hiring Overmars would be he almost surely wouldn't come before summer 2022 when his Ajax's contract expires and we should start preparing for next season sooner, possibly by negotiating with some players on expiring contracts when possible in January or risk losing them. Sure, Alemany can also do that and I have feeling Xavi will actually be the one who will decide about most transfers but we really need some stability at this crucial position so really hope whoever will be hired will be the right man for the job and stay for next 3-4 years at least alongside Xavi. We can't continue to change coaches and SDs every year.
Another thing to consider is if we won't (again) have too many cooks in the kitchen (Xavi, Alemany, Cruyff, whoever next SD will be and obviously Laporta will have some say as well; and this could also be one of the reasons why Planes has decided to leave; possibly going to a club where he'll have a more important role).
This alongside no consistency in planning etc. was one of the reasons for our downfall in recent years. Too many decision makers with no clear role and hierarchy. Not saying they were always on different sides but I'm sure there were some obvious disagreements between all the people going through our sporting department which they couldn't work on so people were just let go and be replaced.
Hope it will be different this time or else not much will really change unless Xavi will prove to be a coaching genius (which we can hope him to be but we'll have to wait and see) being able to do much with less. He'll have to do that anyway due to financial restrictions we are in and will probably be for a few more years at least but he should also have more support than most of our past coaches. Whatever we think about them I believe they could all do better working in a better/more stabile environment. But OTOH this is Barca (where you are in crisis after every loss) so every coach who will be here long enough will have to work through moments of chaos or crisis (the worst thing is most of those are self-inflicted) at some point.
Everybody was expecting that Planes will be gone after the election of Laporta because he is Bartomeu's man. Surprisingly, his contract got
extended for 2 years by the new board as Laporta and Alemany were convinced by Planes' work in the sporting structure of the club.
Now we have to wait and see how he will be replaced, as his departure comes very spontaneously. It could be that Xavi will play a much more prominent role in the entire sporting field than has been the case in the recent past. At least that would have been the original plan under Font and the departure of Planes a few days after the engagement has a certain aftertaste, after it was repeatedly reported how satisfied Laporta, Yuste and Alemany are with the work of Planes. If they replace his position with Jordi Cruyff, who already works at the club, it indicates to me that Xavi is assuming a more powerful role. Might also be that they don't even replace Planes at all (not even by placing Cruyff formally there). Can imagine that Xavi and Alemany will directly work together and divide Planes' competencies between them. Might be a good answer to Bartomeu's labor turnover in this position. What's more important is that Xavi, Alemany and a possible new candidat (if even) have the same plan. Anything else will lead to a clash of roles and the club paid painfully for it in last few years or like you named it: Too many cooks in the kitchen.
I like Overmars, but I don't believe he is in the mix or even interested in the role of the sporting director. He works a tier above at Ajax and this would be Alemany's role. I doubt that Laporta axes him already after one year as he played an important role in negotiating last summer.