Spinning up new SFDC and Marketo instances - collective wisdom

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Spinning up new SFDC and Marketo instances - collective wisdom

I'm seeking the collective wisdom of the community... thank you for your inputs!

After a merger where both companies have SFDC and Marketo, there are major changes in sales and marketing processes. Therefore, a brand new SFDC instance and new Marketo instance is being deployed. It is a 3 month development effort where the plan is that all of the (significant) SFDC development will be done in an SFDC Sandbox instance. The SFDC team has said they do not plan to push anything to SFDC production until very late in the 3 month cycle.

We have new Marketo production and sandbox instances to use for this rollout. We can certainly pair the Marketo Sandbox to SFDC Sandbox but I'm concerned about having to move everything over from Marketo Sandbox to Production so late in the development cycle. 

Does anyone know if it is possible to have Marketo "copy" a Marketo Sandbox to Marketo Production? I've heard of it going from production to sandbox but not vice versa. 

The only references I've found on this indicate that people had to recreate what they did in Marketo sandbox into production which is a significant amount of resources (and possibility for error.)

Any advice you can give on how to approach this would be appreciated!