I already own M&M: Heroes VI - Shades of Darkness standalone version in Ubisoft Connect, which is already almost the Complete version. Neverthless, I'm not a fan of Ubisoft practices concerning both DRM management in itself and how it's aplied to older games. We are always on the verge of server shutdown at any moment, losing access to a full game or parts of it. Already the only M&M: Heroes VI version available in Ubisoft store is the base one, no Gold version, Complete version or any other standalone, leaving potencial buyers (and those that already bought them) without a full game.
I have my Heroes of M&M 2 Gold and Heroes M&M 3 Complete in CD. I own Heroes IV Complete and Heroes V Complete, bought right here on GOG. I'd buy Heroes VI and Heroes VII if available here on GOG too, both of them were bought by me in Ubisoft Connect (store), if you made them available here, full/complete games, DRM-free.