Why should the miners want that?
To support fee-free economy. To show that this is achievable.
Even if they did set up one and every miner switched to those trusted gateways what's gonna happen to the transaction that the gateway drops.
And the same question what will happen to tx's that those gateways doesn't relay would those transactions just simply float and never confirm(if so good for me don't ask why)?
They will not even be counted as a transaction. The balance will still be in the sender's wallet.
In order for this, not only miners but also all coin holders should trust the gateways, though. It makes everything a bit somewhat semi-centralised, but still what I am asking is whether it's doable or not.
In the original "Bitcoin" paper, the first network action is written as "New transactions are broadcast to all nodes" (Section 5). Now, there will be one step prior to that; the transaction request is signed by a zero fee gateway. So it would be like a multisig wallet, one signature of which is the signature of the gateway server.
Spam would just get confirmed by other miners.
OK, just make it obligatory for the entire network to use the gateways. I am just trying to see whether that is something achievable from a technical perspective. Whether or not we
should do that is another question.