>> a company might pay each member a bit more for a team experienced in working together, as in theory they should be more productive more quickly.

On the other hand, if you already have an established team, merging them when they see themselves as distinct groups might be tough.

The other issue I see is that I doubt companies will want this to become common in the industry. Even if it's great for hiring (and I think it often would be - especially for new projects), do you want support something that might encourage a group of all the employees in a particular specialization to band together and decide they want to all leave at once? I wouldn't. Especially since that might happen right at the time when new development is slowing down and deep knowledge about the current system is the most valuable asset related to the project.