Thanks for the idea. I got it working using your concept.
For reference for anyone else wanting both themes available in a multi-site install;
1. Fully installed and activate the Evolve in the network-admin plugins section.
2. Fully installed and activate the Alora in the network-admin plugins section (this replaces t4p-core plugin with a slightly different variant)
3. Extract the Evolve theme on my local machine and rename folder \library\plugins\t4p-core\t4p-core to \library\plugins\t4p-core\t4p-core-Evolve
4. Edit t4p-core.php /* Plugin Name: to Theme4Press Core Evolve …
5. zip this plugin and uploaded to my wp-content/plugins folder then unzip to it’s own folder (should be t4p-core-Evolve) .
6. Now deactivate the Theme4Press Core plugin in the network-admin plugins section.
7. For each specific site under its own plugin section you activate the appropriate plugin based on the theme you want.
Thanks for the great theme – I look forward to having this integrated so that future updates don’t become an issue for me.