imswear, SN:R is pretty much what you need here.

Quote:Version 2.8.7
[+] Added new ERM command SN:R^old resource name^/^new resource name^, redirecting lod/pac/mp3 resources to other names.
    The command is a thin wrapper over RedirectFile exported function. Pass empty name as new resource name to remove
    redirection. All applied redirections are local, stored in saved game and reverted on map exit.
    '*.mp3' redirection works on all mp3 files at once.
   
    Example:
    !#SN:R^crgrif.def^/^croc.def^; let Royal Griffins look like Rocs (portraits are not changed)

    Game unloads not used resources, thus many resources can be dynamically redirected during playing.
    If resource is used in Hero Screen, perform redirection before Hero Screen is shown (and resource is cached).

    Custom interface skins may also be implemented, allowing user to switch themes right in the game (saved game
    loading may be necessary for visual update).

Note:
1. OnEveryDay executs at the start of a turn
2. SN:R has to be executed before a resrouces is loaded