I concluded that this system has a similar security model to plain PoS, since identities never get 'consumed' like they would in a PoW chain. I'm not sure if this is similar to your design?
Although the design has not yet been completed (it's about half-way there) what I have envisioned doing with regards to accounts is to have a regular need to provide a difficult (and memory exhaustive) POW so that you can't create Sybils without incurring more and more POW.
In my design, this was also true, but I realised it was exactly equivalent to buying stake in a PoS system; once you have your identity, you have a constant probability of producing a block, therefore a constant cost for attempting a double spend.
I was looking to design a system with equivalent security to a PoW chain but with improved confirmation times, so I stopped exploring at that point.