Although the batting coach conceded the new lineup, in which the playe

IMO C:
agreed to the new lineup, in which the players’ strengths were better utilized, he said that future lineups must be agreed upon by all managers before being put into practice

A has they error
B them error d & E they error
IMO C is correct

Although the batting coach [url]conceded the new lineup, in which the players’ strengths were better utilized, he said that in the future they must be agreed upon by all managers before being put into practice.[/url]

A. conceded the new lineup, in which the players’ strengths were better utilized, he said that in the future they must be agreed upon by all managers before being put into practice

B. conceded the new lineup, in which the players’ strengths were better utilized, he said that future lineups would require the consent of all managers before putting them into practice

C. agreed to the new lineup, in which the players’ strengths were better utilized, he said that future lineups must be agreed upon by all managers before being put into practice

D. agreed to the new lineup, in which the strengths of the players were better utilized, he said that in the future, they must be agreed upon before having been put into practice

E. agreed on the new lineup’s utilization of players’ strengths, he said that in the future the lineups must be agreed upon by all managers before they have been put into use

C is the best answer in my view.

In A and D, the pronoun they does not have a logical antecedent. The only plural antecedents are players and strengths, both of which does not make sense in the sentence. We can eliminate A and D based on the pronoun error. In addition, the use of having been put into practice in D is incorrect. having + past participle is used to express an earlier action, and clearly, the use of having been is the wrong verb tense in the context of this sentence. This is because we expect before to modify an action that precedes a pre-condition expressed earlier in the sentence.
In B would require is not appropriate to express a desire in the real future. Would require is okay when expressing a hypothetical future or the future of the past, but unfortunately, that is not what this sentence is about. The coach expects that in future lineups must be agreed upon by all managers. Based on the wrongful use of would require, we can eliminate B.
In E, before they have been put into use is incorrect. The use of the present perfect tense have been is unjustified. We can eliminate E based on the use of the wrong verb tense have been. have been suggests that before modifies an action that has already commenced and still in effect, but this is not the case. Before per the context of the sentence modifies an action that will occur after the fulfillment of a requirement.
We are left with option C as the best answer out of the lot.

Although the batting coach conceded the new lineup, in which the players’ strengths were better utilized, he said that in the future they must be agreed upon by all managers before being put into practice.

A. conceded the new lineup, in which the players’ strengths were better utilized, he said that in the future they must be agreed upon by all managers before being put into practice

B. conceded the new lineup, in which the players’ strengths were better utilized, he said that future lineups would require the consent of all managers before putting them into practice

C. agreed to the new lineup, in which the players’ strengths were better utilized, he said that future lineups must be agreed upon by all managers before being put into practice

D. agreed to the new lineup, in which the strengths of the players were better utilized, he said that in the future, they must be agreed upon before having been put into practice

E. agreed on the new lineup’s utilization of players’ strengths, he said that in the future the lineups must be agreed upon by all managers before they have been put into use

NOTES: intended idiom is "AGREED TO"

(AB) "conceded" unintended;
(E) "agreed on" is unidiomatic;
(D) "the stgs of players" is less concise than the active "ps' stgs"; also, "they must" pronoun ref is unclear; "having been" is unintended;

Ans (C)

Answer must be C for
1. not using the wrong idiom concede rather than 'concede to', as in A and B
1. using the correct idiom 'agreed to" and
2. not using the wrong tense having been and have been as in D and E,

Agree with A-D
With E, I think there are two issues
1. What the coach conceded with has changed
2. 'they' isn't correct.

It is more that just wordy and awkward, there is a change of meaning and antecedent problem.