Hi,
You cannot change the filesystem names as you wish, this won't be supported as it is documented in Oracle E-Business Suite Installation Guide... If Oracle says, "don't give a full path for the directories", than it means it wants to a specific subdirectory names for its product. So as fs1 and fs2 are subdirectories, this means "you can not".
With this information, even if it technically seems to be done after the installation", you should not do it, as it is not documented and its affect can not be predicted. (there may be hardcoded fs1 and fs2 somewhere in the code)
Using Rapid Install, Rapid Install needs to be told the locations of the top-level directories and mount points on the database node, and the Applications node(s). It derives subdirectories from these top-level directories.
Important: Only the values for the base directories can be specified. The derived values for other directories must be left at the default values that are calculated by Rapid Install.