Are you saying He does it with foreknowledge or forethought. If He does so without foreknowledge, then He is not God. If He does it without forethought, then He is not doing it with foreknowledge, and He is again....not God.
Therefore, He did it KNOWING the person, and THEN it was His pleasure....in other words He was pleas(ur)ed with the one He chose and NOT pleas(ur)ed with the one He did not choose.
Therefore, it was something in the persons that He knew that either pleased Him or displeased Him.
You are correct that He must necessary have knowledge of the person before He can choose that person. However, you are making two critical errors here:
1. When saying that He "chooses according to His good pleasure" it is meant that He chose as it so pleased Him to choose. That is, He was pleased to make the choice He made. It does NOT necessarily mean that He chose based on some pleasurable attribute of the person. It simply means that it pleased Him to choose as He did.
2. He is not pleased by the object of His choice (that is, in the transitive sense) but rather pleased by the choice itself.
Therefore, it was something in the persons that He knew that either pleased Him or displeased Him.
See above.