Tomatoes are already pretty acidic, and usually you're trying to mellow that out a little bit. You hear splash of balsamic sometimes, but that's more for some complexity than the acid.

The sugar wouldn't be bad, in moderation, but I'm thinking pineapple has a bit too much. If you added a bunch of pineapple for any reason, you'd have to bring it back into balance with other things. You're really departing from spaghetti and meatballs now, heading in an almost SE asian direction.

By the time it tastes good, it won't be very italian anymore. Probably one of the legit worst cooking ideas I've heard in awhile, I'm having a hard time thinking of a more ruinous ingredient to add to an Italian-American red meat sauce.

You know, when you put it on pizza, there's usually ham and jalapenos too. Those are balancing elements, both very strongly flavored.