Since I run my own Gitlab I don’t have to care so much about the licensing.
One big issue with not committing the imported assets would be that you can’t easily track if something you did in the Unity editor happens to clobber some of the stuff inside the assets.
When moving imported assets into one folder (which, depending on how you want to deal with that mentioned “asset data got changed sideways” issue above, could be added to the .gitignore list), things to keep in mind might be that some of them don’t like any changes to where they’re placed in the project, too. And updating to a newer version might not detect which items were changed and which were not (and you might want to make a commit that specifically mentioned what the asset’s update changed)…
So in an even bigger project it might be a good choice to just add a folder in which to place all project-specific things one might add (one’s own assets and scripts)… 