I think the reason the game doesn't have escort missions (in either direction) is twofold. First, if you have two fleets that are supposed to move together, one can get distracted and wander off, or get into a battle without the other, or do any number of janky things that would be unpleasant to have to work around. Second, given that "fleets" are essentially an arbitrary construct - just groups of individual ships that decide to move and fight alongside each other - an "escort" is substantially more effective if it just joins your fleet directly.
That said, it could be interesting to have commissioned and player factions offer some ships and officers to the player as a quick, cheap, immutable bundle, rented at a discount and less expensive than normal to lose. This would serve the same purpose without the risk of jank - sort of like Nexerelin's mercenary packages.
For example, the Hegemony has a tough bounty, and they want the player, who has a Hegemony commission, to take it on. His fleet isn't strong enough to do so alone, so they give him the equivalent of a heavy patrol worth of non-customizable ships and officers for the duration of the mission, with a fraction of their cost being deducted from the payout when it completes if they are destroyed. Lets early and midgame players get into harder fights with reduced risk, and also lets players feel like they are meaningfully part of their selected faction.