Ghusl When The Time Is Running Out
In principle, the secondary form of any ‘ibadah’ is undertaken when there’s undue hardship (mushaqat, usr). What constitutes a hardship is left up to the individual. If someone overslept by mistake, the salat that they offer after waking up is not ‘qadha’ to begin with. Instead of ‘wudu’ if ‘ghusl’ is required in order to perform the salat then ‘ghusl’ should be performed and the salat will still be ‘ada’, not ‘qadha’.