The subjunctive mood is the best.
The subjunctive is rarely used in colloquial English. Totally irrelevant information, but... it is a relic from Latin, where there are many uses for a subjunctive. There is even a special conditional using the subjunctive mood that expresses the exact circumstances you described, which is usually called future less vivid.
A global citizen is someone who self-identifies first and foremost not as a member of a state, a tribe or a nation, but as a member of the human race, and someone who is prepared to act on that belief, to tackle our world's greatest challenges.
