Triple Masques was a horrid format and rebels were absolutely miserable. Being able to sink mana for progressive huge amounts of card advantage was just plain more powerful then what anyone else could do in that format and some of the cards they could search for were
just stupid. Nothing else you could do in the format could go under the engine or keep up with it, making every game a grind to victory.
However, in cube this all changes. We don't have to include bullshit cards that you can search for. Decks are fast enough to go under. Sweepers are as plentiful as we want them to be. The finishing creatures can still take over the game in the face of an accumulation of rebels. We can select interesting cards to search for. It wouldn't completely overshadow every other strategy. And most importantly, it would give white a different, unique angle to go with. There is such a thing as a pleasing grind and I think, well selected, Rebels could fall in their.
I think on a high level its a fine idea, but the realistic matter of actually figuring out how to tag the cards is pretty tricky.