Just like an Alien Data Disk gives just research, couldn't there be artifacts that grant research strait into a research tree?
Missions Like the Shield Strength Test could reward Shield Test Data that grants research in only the shield research tree.

What if they've finished that research?

Then it would automatically go towards the "research to credits" that high level players have been talking about.

They might not've unlocked that though; it doesn't come from just finishing one line of research. I guess it's fine, but it would need to be a better ratio, if its an artifact drop, than Alien Data Disks, and would need some method of dealing with people having already completed that particular line of research.

Not really. They can save them for future tiers.

Then it would need to not let them use it if they've finished the line. In some way it needs to deal with someone having already finished that line of research.

Lots of ways it could deal with them having already finished the line - flow over into a related line that's unfinished, simply not activate, waste the points into the ether, exchange for credits, etc.

Which of those the Devs pick is up to them - and likely subject to which way would be easiest to program and/or which would least damage the game balance.

Personally, I kind of like the idea.