By fee-less mining I mean no fee AND no block reward. You can't pay anyone anything. Can't outsource to a third party. Otherwise fighting breaks out.. and in the end.. There can be only One (You know this..).
As far as I can see, without fees, any system would be vulnerable to DoS attack. Got any reference to prove me wrong?
A system like IOTA.
The work is the fee. (But not IOTA - as it has it's own quirks. Something new.)
No block reward & no fees <==> tangle (IOTA)
It is true specially considering your underlined(by me) phrase: the fee being the work
IOTA and tangles are out of context. Let's put it this way and stick with our plain old blockchain technology. Note that eliminating transaction fees alone and keeping block rewards or vice versa, won't help your argument about de-incentivizing centralization attempts in bitcoin.