In my opinion, on one hand, before issuing NEM, the users should be as many as possible.
On the other hand, we should have many markets to buy/sell NEMS at the same time when starts transaction.
addition, if we can develop one platform which can exchage NEM with any other coin(not only btc/ltc/doge) ,we can distribute the coin widly.
Also, if we can develop a platform that allows fiat money to be exchanged for NEM, that would allow a lot more people whom are new to cryptocurrency to purchase NEM. Some people don't want to go through the phase of first downloading a wallet, signing up to an exchange/website, purchasing BTC or some other cryptocurrency, then purchasing NEM afterwards.
Yes. This is one of the most important aspects to focus on. Other than the development of the coin itself, I can't see anything more key to mass adoption.