However, if majority users use it and if it becomes the larger chain, it maybe considered as main chain.
It only starts producing larger blocks with a mining majority of 75%, so it's always on the main chain.
You mean an ostensible "75%." In reality, it would be lower. BIP66 thought it had "95%" support, which in reality turned out to be 64%.
The more bloated the block, the more likely an empty one will be produced while new tx are verified (which defeats the purpose).
HearnCoin is rubbish; it wouldn't even make a good side chain or alt.