Thank you for your feedback. We’re considering this for a future release of Azure Search.
Azure Search Product TeamCorby commented
Unable to figure out how to go from S1 to S2. We need to open up the additional search indexes as we have maxed out our 50. There appears to be no way to do this within the portal. I've created a support ticket to ask for an Azure tech to help. It takes 2 seconds to resize a VM to a bigger box, I thought upgrading Search would be a similar procedure.