What would make Rey a better character?

Actual character development would be a start.

That sounds haaarrrrrrrrdddddd. What if we just showed her beating up on a beloved legacy character?

Just make her evil. Everyone hates her already, might as well cash in

some struggle and hardship. like she shouldnt even put up a fight against even a wounded kylo in the first movie. fuck, 2 newbies didnt cut their own fucking arm off with a weightless lightsaber and went full samurai showdown against a trained sith lord. its retarded how strong she is and how perfect with no training or effort. she learned and mastered jedi mind trick after seeing it done once and resisted all mental probes and beat back kylo. thats mental and physical domination of the main villain of the first movie and set up as new darth vader. theres no coming back from that kind of premise and she just goes super saiyan in the next movie lifting mountain of rocks and everything they did to luke and so on. the problem is they cnat have a woman get beat the fuck up. no one wants to see her have her arm cut off or lose her legs or get her jaw sheered off from a lightsaber in a battle she has no reason being in yet. no one wants a cyber woman protagonist. this leaves you with only a perfect protagonist that cant be harmed or lose and never struggle.

The movie would have been better if they just flat out removed her

Make her a man

Full penetration. By Aliens.

Dark side.

A dark side arc. She grows up in poverty treated like shit and the new republic instantly becomes corrupt like the old one which didn't care about slavery on Tatooine and sidelines the Skywalkers who are fighting a losing political battle and have virtually no influence.

The Skywalkers admit they failed and predict someone like her will arise and kickstart the process of the Sith rising all over again.

We see her journey, she did not wake up and decide to be evil, rather she is traumatized and decides upon helping the weak, she starts off fighting against thugs and criminals to defend the weak, she then climbs the ladder, leading a revolution, but slowly along the way she learns how ruthless she must be to have any success and change the world and this corrupts her.

Eventually her power rises and she now controls a ragtag military force that now controls her world. She ends slavery, however she now taxes the planet and controls everything to an insane degree, people still have little freedom and still live in poverty because everything must be sacrificed to her cause. After all they are just 1 inhabited planet out of millions, their inconvenience doesn't hold a candle to the plight and suffering of the rest of the galaxy. This sort of insane control freak ideology is the dark side manifest.

This attracts the attention of both the Sith and the Skywalkers. Kylo Ren who has jedi powers, but weaker than his illustrious family, is sent to investigate the uprising and concludes he must defeat her to prove himself. Adam Driver and Daisy Ridley, initially adversaries, develop immense sexual tension, eventually Kylo turns her to the light side. The Jedi are restored and play a more active role, Rey realizes you can't control everything while the Skywalkers realize you shouldn't give up on good causes and trying to make a difference and they finally solve the shitty government and sith problem

he shouldve been Obiwan's granddaughter and not show any kind of force power till the second movie, she would then fall to the darkside and be redeemed in the third one.
Also let years pass between movies, it was ridiculous.

Basically this. Rey is not a character, she is a walking plot device at best.