I looked through the API and talked to developers, and there is no way to add skills to the voicemail callback without first using Transfer to ACD to send the call to a queue. There is no way to use an In-Queue Call flow to send the voicemail to a different queue. So, no way to accomplish what you want, currently.
Please submit an Idea on the Ideas Lab (linked from the Genesys Knowledge Network dashboard or at
https://purecloud.ideas.aha.io/ideas)
Product Management is aware, and will take a look at seeing if it can be added to the roadmap.
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George Ganahl CCXP, GCP
Principal Technology Consultant
Genesys
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