Edit: also I can devise an attack to side-step your protocol rule. Build a chain branch that has no double-spends and make it public. Gradually change my list of witnesses one-by-one on the units I sign as the old witness happily sign units on my chain branch to advance the stability point. I can spam with as many Sybil address signed units as necessary to convince the witnesses that my chain branch is "real". Then once I've got the old witness down to a minority, I can take my chain branch private and complete the attack I explained to you before.
Again, seems like you are assuming you can convince somebody with the number of your Sybil units. And not just somebody -- the acting witnesses. The acting witnesses, and other users likewise, are not going to change their own witness lists to stay compatible with your Sybil units. Your Sybil units will be accepted into the DAG, but, being incompatible, they are not going to be selected as
best parent, hence they have no chance to appear on the MC, hence none of them can ever become
last ball (which necessarily lies on MC).
Okay so you are telling me that the current witnesses on the branch I am trying to create have to agree with 11 of 12 with my list of witnesses when they sign units on my branch? So this means the entire system has to agree on the
same 12 witnesses for all main chains for the entire system?
If that is your design, then yes you can prevent my attack but at the cost of having 12 very entrenched witnesses which can never be migrated away from because political action never reaches 92% agreement.
So why not just use 12 federated servers and name this Visa, Mastercard, or Paypal instead? No need for the facade of a DAG nor to claim/insinuate by association to our Satoshi ecosystem that it is decentralized. Distributed is not same as decentralized.