The purpose of STP is to create a redundant loop-free topology in layer 2. If you're operating from the assumption that the network won't change, you might as well just make it loop-free in layer 1. You're free to pursue any design, but you requested...

You would be subject to this bug which only affects non-root domains with peer-switch: https://bst.cloudapps.cisco.com/bugsearch/bug/CSCwa83042The defect was never and likely will never be fixed because the design [peer-switch on non-root] is unsuppo...

Pavel is correct.Note: The vPC Peer Switch enhancement is only supported on a vPC domain which contains the root for all VLANs.https://www.cisco.com/c/en/us/support/docs/ios-nx-os-software/nx-os-software/217274-understand-virtual-port-channel-vpc-en....

Ravi,   Generally speaking, anything not listed in Table 2 would be supported without a license: https://www.cisco.com/c/en/us/td/docs/switches/datacenter/licensing-options/cisco-nexus-licensing-options-guide.htmlEric