Hi,
If you are fine with NUC, you can continue with NUC in 7.31 after the Upgrade, so no UC conversion is necessary.
For the modeling of the SEM Add-On there is now a new and better solution available to handle the SEM Add-On as a pure NetWeaver Add-On (not ERP component anymore).
See the Blog on the BW ALM Page - SAP NetWeaver BW Application Lifecycle Management (ALM)
Best Regards Roland