You know, you're definitely going to get accusations of being an X-Com2 clone if your mechanics and even missions are so similar to it. I don't think it would do anyone any good if such copying came about. There is no reason not to involve a little more creativity for something different.
For example, instead of the "Assasinate VIP", you could simply call it "Disrupt Alliance meeting" (An alien negotiator is meeting with a leader of a separatist movement to discuss an alliance. Ensure that neither of them survive.) and have a mixed enemy force of humans and aliens that you have to fight.
Bombing Stock Exchange: In order to cause economic disruption, aliens have begun attacking financial centers. If something is not done, the economic downturn will cause a loss of funding to the Xenonauts program and dissatisfaction with our progress.
Escort Tech Transfer: (Possible strategic option with new tech discovered, limited to new weapons and armour): To increase the effectiveness of local forces to resist the alien threat, Xenonaut HQ has decided to release their findings of alien tech to the world governments. Ensure that the transport reaches its destination (can be an air defence mission, ensure a helicopter reaches country X without being shot down, or a land transport mission), relationship bonus if mission is successful.
Invasion!: Aliens have set up an invasion base to militarily conquer Country X outright. Local forces are holding their own for now but casualties are mounting and panic is spreading. Help them by taking out strategic targets protecting the alien base and causing their position to become untenable (random missions can be between taking out alien artillery, alien air defences, alien power plant, alien leadership, open a breech by cleaning out all aliens in an area or blowing up invasion base power plant, so many possible options).
As you can see, there really isn't a point in courting accusations of plagiarism or copying when there are so many more possible other routes to choose from. It does Xenonauts a disservice to be seen just as a copy of something else.