The optimization attack can be avoided.

Require 1000 samples of the work.
Reward those contributions within a 30% variance of speed.
Use the fastest speed as the reference for what the work is worth.

In bitcoin the longest chain is the accepted true chain.
In Noocoin the fastest work should define the worth of the work.
This will also behave as a fast adapting difficulty parameter.

Result: No trusted nodes needed.