Thanks for this, its nice to have something of a roadmap going forward.
My feedback:
#2-5 look good.
Regarding proposal #1:
This seems to me to be a very complicated solution which requires additional code to get around spamming.
Before we do this, do you really think that an order fee of 0.1 BTS instead of 0 would not be sufficient to achieve these goals instead?
Imo, the problem with the perception of the fees for orders is because they are currently large, but 0.1 BTS would probably be small enough that this would no longer be the case. At 0.1 BTS, the attacker would have to pay to fill up our TPS with spam, but the fee would seem negligible to traders. A percentage based fee for trades of 0.2%, plus a 0.1 BTS fee per order (cancelled or not), looks good to me.
I do not think that a 0.2% fee +flat 0.1 BTS would feel different to users than current crypto exchanges.
Could you discuss your thoughts on needing to implement this new system rather than simply change the fee for cancelled orders to only 0.1 BTS? Are you really sure that a chance to just 0.1 BTS would not be sufficient to solve the problem, or that it would still be perceived as a problem by users?
Thanks!