Late Gloria Foster died of diabetes on September 29, 2001, during the shooting of Reloaded. The Oracle was a central character and thus the role was kept, continued to be played by Mary Alice. The Matrix franchise tries to put an in-universe story around this change.
I cannot help but feel like the Oracle switching shells were only put in due to her death. Is there any proof pro or con this?
Some screen time in both Revolutions and Enter the Matrix deals with the issue and it's unclear whether some of the scenes were added completely or changed heavily only for this issue. If the whole shell thing were added later than it is more significant. The plot change may involve at least Rama-Kandra, Sati, Kamala, the Merovingian, Neo, and maybe many others (Niobe, Ghost, Seraph, Trinity, etc.)m potentially modifying the role of these characters, too.
How much impact the change in the role had on the plot?
Were there other scenes planned with the Oracle for Reloaded? What was the original plot of the franchise?