Isn't that in C# now too? At least, for individual player-owned colonies?

I couldn't find it when I looked, but maybe I didn't look in the right place.

Absolutely.

VB Aurora had a "Give Colony" button that would transfer everything to another empire.  I sorely missed it in C# Aurora, because it was my default method of amalgamating two species at game start to get a multi-race empire.  Create Race A, choose neighbouring planet, Create Race B, Give Colony (B's homeworld) to A.

One feature of 4x games in general that I sorely miss is the possibility for two allied empires to combine into a single empire.

As of Aurora 7.10, we have an "Independence" button to declare Colony Independence, which allows us to create a separate state or empire. And there are plans to "add the possibility of independence due to high unrest."

But how about the reverse? Why can't we combine empires? Of course, this could have roleplaying potential for combining two player-controlled empires. But I was thinking in terms of NPRs.

Specifically, with enough positive relation modifiers via diplomacy - assuming the other race has a similar form of government - why can't there be a possibility that they join your empire or form a new, combined empire under player control?

Before someone claims how absurd the idea is, I would point out that there is a historical precedent where nations have combined. Unless you're an ardent student of history, some of these will surprise you:

Historically, which nations have peacefully agreed to merge to form a single nation?

And even in today's political climate, there is still a possibility for nations to merge.

Which two countries today could merge into one peacefully?

It sounds like it's only a matter of time before North and South Korea recombine. And, in a matter of decades, China is poised to absorb Taiwan, Hong Kong and Macau (perhaps among others). There are reasons to believe that Belarus will some day join Russia.

Okay, granted: By bringing up NPRs I'm talking about aliens, presumably merging (politically or at least through military, research and industry) with a fictional Earth empire. But is that really so absurd? Did we think that Star Trek's Federation was an absurd idea when we were first introduced to the franchise? Or what about the Old/New Republic or the Rebels in Star Wars, with humans fighting alongside and sharing political seats with other races?

But even with existing diplomacy mechanics, with enough relation modifiers, an allied NPR will allow trade access, defend player assets, and share research. Is what I'm suggesting that far of a leap?

Consider, too, how each race can already have several sub-species, genetically modified for different planetary environments. So it's not like empires don't already have to deal with the potential for sub-species discrimination and such.