But in possession of invaluable skills and knowledge. It's interesting that Data was the only TNG character never promoted or offered promotion. Here's another way that could have been fixed, in "The Offspring"...
PICARD: "It would seem you've actually improved upon yourself, Data."
DATA: "Is that not the goal of every parent, sir?"
HAFTEL: "But as a good father, don't you think it would be better, especially in light of this new aberration, if Lal were close to people trained in diagnostic and evaluative procedures?"
DATA: "I am programmed with the procedures you mention, sir. And in any meaningful evaluation of Lal, you would require a model for a basis of comparison. I am the only model available, Admiral."
HAFTEL: "Indeed. And that's why we'd like you to accompany Lal back to Starfleet Research. Your experience and expertise would be invaluable."
PICARD: "The Admiral is offering to make you project lead. This posting would come with a promotion to full commander. As well as the opportunity to work with some of Starfleet's foremost experts on artificial lifeforms."
Even if it didn't happen, if Lal suffered systems failure before this step could be taken, and Data chooses to remain on the Enterprise, it at least shows that the offer was made, as with Picard and Riker.