Remember other developers who dump premine and vanish? Not me, I give it away and mine like everyone else. Making the coin too fair backfired though, and im sorry.
In the OP you mentioned a beta of the ad system in 3 weeks. Are you planning to do this work yourself or outsource it? The pre-mine would likely not go very far for the Dev work needed.
Most importantly......do you have the resources to see this through as it sounds like it will require a great deal of time. It would be much more challenging if you are working on it on the side or when time permits. If you cannot follow through with the plan in the OP for whatever reason letting it go to someone else may be best.
I agree with above, a clear direction is very important for many. (not all that may only be in it for 21 days or less)
Bittrex is gonna massive stake this coin, I wonder where those coins go? Could they be released to OCminer for premine, and used for promotions?