Making a cremeaux lighter with whipped cream. Is there a name for this?

The name for this is still 'cremeaux', nothing changes.

In English pastry jargon, "cremeaux" is a (somewhat rarely used) umbrella cream for any sweet filling with a creamy consistency. It is not connected to a specific recipe or technique. If the thickness is such that you can pipe it, and the texture is more similar to a custard than to, say, jam, then it can be called a cremeaux.

An alternative word for a substance of this consistency is "cream", as in "buttercream" or "shaving cream". The difference is that it is also used outside of the culinary context, and when it is used in culinary language, it can be confused with "cream" the dairy liquid made by partially removing the water from milk. I suspect that some people use the word "cremeaux" to avoid the confusion, and others just because it sounds fancier.

So, if you take a random recipe that can be called a cremeaux, maybe a custard of the right thickness, and then fold whipped cream into it, you still have something that is sweet, pipeable, and creamy in mouthfeel. Which makes again the word "cremeaux" applicable.

Depending on the final texture, the result may also fall under the term "mousse". The mousse's central characteristic is that it is very airy, while still spoonable. If you added a lot of whipped cream, and managed to keep most of the air in, it may be recognizable as a mousse.