Well you have to differentiate the main purpose of both solutions, Outbound and Proactive with GVP. GVP will dial by itself, the fact that you can use OCM to handle the data is a plus, the main target of this solution is to dial automatically without agent intervention therefore agents stats are not taken account when dialing, only free ports. On the other hand Outbound solution (OCS) is the application that dials to customers considering that on the other side are agents waiting to answer that call.
Now you want a mix of both, but think on this way, how many of these contacted customers will ask for an agent? Everyone? A few? What are your predictions??? If a few then modify your business needs to reserve an agent group to attend these possibles interactions with them. This will obviously sacrify some resources (agents) due the fact that maybe no customer will ask for an agent. Modify your business strategies to find the most suitable configuration for you.
If on the other hand many customers will ask for a live agent...why use automated ivr messages? Customers hate the fact of a sale promotion using IVRs, better will be to have a live person on the first attack. Even if you dial on this way using progressive mode customers may find a small queuing...
There are pros/cons on both sides but you can't achieve your ideal scenario, not doable...
Other idea would be for example to show the customer the agent option only if you have free/logged agents but will maybe not accomplish your needs.
Learn a little bit more on the focus of both softwares and find the best for you