Implementation of special units into older civs

In this post I'm referring to specifically the Battle Elephant and Steppe Lancer, however with any potential future additions I'm assuming there will be more. Both units were added exclusively to a pack, yet I think it would be nice if they gave these units to older civs as well, not only for balancing reasons as they could offer a little help in that area, but also because it would make sense.

One obvious one in my opinion is giving the Indians the Battle Elephant or some other camel heavy civs the Imperial Camel, which doing both would work together fairly seamlessly anyway. Another I'd more hesitantly do that also makes a lot of sense is giving the Mongols the Steppe Lancer.

There's no reason to make units exclusive to the civs in the pack they came with, especially when the units could fit in better with an older civ.