How about an event for making a primitive species you're observing adopt your gender laws.

- A specific gender suffers from short-term illness (applies penalty for X years).
- A specific gender suffers from long-term illness (requires storyline cure).
- A specific gender is abducted by aliens permanently.
- A specific gender is abducted by aliens but returned (and altered).
- Adam & Eve abduction -- a population is abducted and placed on a new world (colonising it).
- A specific gender gains a positive trait.
- A specific gender gains a negative trait.
- The male gender becomes sci-fi parasitically "pregnant" (think Aliens).
- Megalomania: A specific individual (leader / scientist / NPC) of a specific gender suffers from elevated self-worth -- and goes rogue -- resulting in their loss / rival faction creation / piracy.
- Gender Specific Piracy: A Pirate Faction is created fighting for loot / independence / their rights.

-gendercentric revolts, like shunned gender wanting the same rights as the other one. Sometimes with pirate ships, sometimes a planet debuff that gives unhappiness and lowers your stability for 3 years;

-an event where a gendered shunned individual have great promisse and if you should or not put then as a leader (like a similar event that can happen whe you have slaved an entire alien species);

-gendered revolts inspired by another empire that have a diferent gender policy than yours, giving you a casus belli against then that is a blend of humilliation and converting then to the same gender policies as you;

-an international envoy was bellitled in your government because they are from a shunned gender, making the other empire dislike you (75% chance) or even insult you (25% chance);

-an international envoy was impressed by your gender politics so much that it makes the other empire like you more (85% chance) or converts the other empire to the same gender policy as you (15% chance)

-an event for monarchic empires were your successor dies, and the only one next in line is someone from a shunned sex.Now you have to choose if you want to keep then and having a empire-wide happiness and faction attraction debuffs until his death/gender policy change or choosing someone from the right gender to be your successor, but then having a succession civil war against a force with 60% of your max fleet capacity when the new successor gets to power. Winning the succession war will give you 30% of the unity needed to the next perk and a faction attraction boost for 5 years.

- Prominent Specific Gendered Leader has sex change, resulting in mass hysteria...yeah I'm probably dreaming :P