I wouldn't say that, FFG has enough resources (brains) to come up with their own ideas for everything. And the possibilities to simulate the rescue of Hera are endless.

Also as the rescue of Hera is part of the series and FFG has the right to put it into expansions, they don't have to be afraid of someone accusing them of stealing ideas.

Especially since I've contacted them, I asked permission to publish this unofficial expansion (non-profit, of course), and to officially surrender any claim to these ideas...

They gave permission to publish, but they declared that they're not looking into outside ideas of any kind.

Meh, I want to be a game designer.

That's pretty much what I expected.

It's not the element of rescuing Hera, but the mechanics involved that I'm talking about.

If they're planning another expansion, and it includes rescuing Hera in some fashion, then they will most likely avoid any mechanic that looks similar to anything already out there. For example, they can't make a board that looks close to yours because they're not going to want fans claiming they poached your ideas. Likewise, your expansion has set an unintentional bar if they decide to bring out a board where rescuing Hera is the goal (unless their designs predate yours, or they're exceptionally badass).

Not saying it'll happen, just cautioning against it. :-)

That being said, I really hope they have an expansion in the works.