Modern Asset Handling - Multiple Projects?

I have inherited a unity project that has not changed drastically in the way that assets have been handled since 2016. I am tasked with modernising the project and converting it to the latest build of Unity.

The current project is made up of two Unity projects, one which handles all assets for prefabs/models and one which plays the main scene and loads these bundles. The working process is to work on the models in one project and then save the asset bundles and transfer them to the other project.

When the scene is loaded there is a significant amount of time spent loading these bundles into memory so they can be used.

I personally can't think of a reason why I would not just use these models and prefabs normally and condense everything into a single Unity project to do away with the faff.

Do you see any downside to this?