Zero transaction fees are no longer feasible. It was calculated with the coin age as a factor a long time ago before it was removed. The inputs amount was also taken into consideration [1].
There is really no point to try to allow for free transactions to be relayed. The mempool is frequently being pushed to it's limits and it's fairly pointless to reserve any of it for free transactions; miners would rather choose the paid transactions.
[1]
https://en.bitcoin.it/wiki/Miner_fees#Historic_rules_for_free_transactionsAha! I knew it existed at one point in time. I knew I couldn't have came up with a novel idea, but rather just pulling it from memory.
Mempool occasionally clears up. I wouldn't mind waiting a few weeks for my transaction to finally be included in a block.
It is up to the miner to choose which transactions go into the block. No miner will pick a 0-fee transaction, regardless of its age, if there are paying transactions to include. There is no way to enforce your policy.
Well, it's up to the network to broadcast the transaction, which is where the issue is currently.
It's interesting there are some blocks where miners will not include any transactions (due to the method of mining). It seems that not validating transactions only hurts the network as a whole. For example, if most miners were to mine this way, no transactions (other than block rewards) would be processed effectively reducing the overall value of the network to nil.