If Efinity will use any kind of PoS consensus protocol, consider allowing users to stake their (N)FT's in addition to their ENJ.
If the user decides to unstake, there could be a delay introduced, so it takes a week to unstake. The items can still be used in games while they are staked, but they cannot be traded or melted.
This way items will become more rare and it would make sense to accumulate common items, since they now can be of value, if you hold enough of them and for a long enough period of time.