He is a pilot, not a mechanic, it's impossible to ¨improve his mechanical reliability¨ because the mechanical reliability of his car doesn't depend on him, this is the job of engineers, mechanics, etc. He do what he has to do in a brilliant way - he gain poleposicions and lead races, but what doesn't depend on him is the reliability of gearboxes, engines, electronics, etc. There are other people well-paid to do the mechanic stuff.
IMO it will be a hard way to go because Hammilton will need some time to get used with the new car and it takes time.