Re: "So someone decided use different battery size for Model 3 "
GM and Nissan got the battery range or PHEVs became mainstream and killed the BEV market.
The PHEV is still mostly large SUV and family cars. The Mitsubishi PHEV is ~ 30k at present. Even for that amount of money it sells like hot bread and is outselling all other hybrids and electric vehicles combined in the UK. If Musk does not deliver by next year, it is pretty much game over at least for the European market, because from 2019 it will probably go downmarket into the small car segment as well.
So he is clearly pushing things to the limit and is doing this not because he can, but because he has to. Anything else aside, he has created some competition in a number of supposedly moribund sectors so this cannot be bad.