I think we should bring back the priority feature back to bitcoin once again. maybe we can even fight the spam transactions with this (to some extent not completely). franky1 had some comment about this.
but in the end it is up to the miners to implement this or not. and since miners are looking for more money I think even if block size was increased and it was empty they wouldn't prioritize low fee transactions as right now F2pool mines empty blocks if mempool is empty and there are high priority low fee transactions in it.