I've found that to make the entourage system work, each NPC only needs about one or two scenes with the party. Thereafter, they can appear briefly and a very short scene and everyone sort of understands that they are there. More on this later.
Background: Ishi is a planetary expert - a dedicated explorer and soldier of fortune who has seen dirtside on countless worlds. Ishi grew up, hand-crafted by a guild of explorers. From the time she was a little girl, she was taught the way of her guild's explorations and techniques. However, her guild was long ago wiped out by the insidious actions of a xenos cult. Since that incident, much of her memory has been wiped out, for in her escape, her ship was lost in the warp for a time. Since her memory loss, she has made a name and life for herself exploring the fringe. Ishi's actual age is unknown to most. She appears to be a young woman but often hints at a past which stretches back at least a century.
Background: Incabula is a navigator with one of the great Nomadic Houses. The circumstances of her joining with the ship Angevin's Blade is not entirely clear, but it is believed that she was purchased with a number of other navigators for the small but significant Baetarn Merchant House. If the records are to be believed, the Angevin's Blade was a guardian vessel for a trade fleet which is now presumed lost to ork attack. It is unclear how precisely her ship was overtaken by orks. She is loathe to speak on the matter and it may be that she does not even rightly remember all of the details. Her mind has blocked portions of the details out.