how can boxing improve

Ideally you would have a board that fixes fights rather than the promoters themselves. It would choose the date, the venue, the fighters, and the money. Take it or leave it.

You would have less cases of ducking out and choosing convenient routes to meaningless titles.

Like Chubble19 said, you would also need better cards. No point paying for a PPV only for the main fight to end in 2 rounds.

Imagine a Haye-Klitschko, Arreola-Klitschko card. It would generate a lot more PPV's, because your average fan would be more willing to dish out money for 2 big fights than for just one. You would also have a bigger fanbase buying the fight. Mexicans and Americans couldn't care less about Haye-Klitschko, but will jump on board if Arreola is on the card, and vice-versa for Brits.

It would definitely be more interesting than Klitschko-Gomez or Haye-Barrett.

There's a lot of room for innovation. You could pit stables against each other (for example a card with Freddie Roach fighters fighting Buddy McGirt fighters), or make it a national thing (Mexicans vs Puerto Ricans, with the military deployed to keep the fans off each others throats).

You could also have knock out tournaments with the top 16 fighters of a division. Round of 16 in January, Quarter-finals in April, Semi-finals in August and finals in December. If it's too tight, you could spread it over a year and a half. By the end, all the titles will have been unified.