I just had a shit-show of a run where I had 3 crew for the vast majority of the game and had no battery and 2 open system slots by time I made it to Sector 8, only buying a drone system along the way. I somehow translated this into a win. 4 shields + Defense 1/Anti-Drone makes you nigh untouchable to the mothership. I used to think that cloak was damn near required to beat the mothership, but now I may opt for 4 shields instead.