Could I control one slave with 6 diferent masters?
In theory: maybe. In reality: No.
The I2C standard documents a multi-master process. This might work if there's usually no traffic on the bus, so you almost never get a congestion. Even in that scenario more than 2-3 masters is probably to much for one I2C bus. I never saw or heard of a real life system where multiple masters worked reliably on one I2C bus.