So three colour plus decks are the big names in the cube at present. Mono colour decks are lacking the versatility needed and two colour decks have no real mana fixing advantages over the three colour ones as well as a much smaller pool of gold power to draw from. Aggressive decks also seem to have the advantage over control decks at present with threats simply being better than the answers a lot of the time.
The idea I had to redress these issues a little is simple but would also have some significant implications. While it would change the format significantly I am not sure if it would be a bad change. The idea is simply that you gain +1 starting life total for every basic land you include in your final 40. This would put most three colour decks at 21 life, you average two colour deck at about 27 or 28 and would allow some mono coloured decks to get to around 36 life. Suddenly splashing black in or red into your UW control deck might not seem like a no-brainer if it is going to cost you six starting life to do so.
The majority of mono coloured decks are not going to be significantly affected by having 30+ starting life totals either. Decks like RDW, white weenie and mono green ramp all tend to win or lose fairly decisively and a chunk of life wouldn't make the difference to a game that often. For the most part I suspect that it wouldn't wildly alter the metagame. Red would be a little weaker but presently it is one of the best colours so no real issue there. The one colour significantly effected by higher starting life potentials is black where suddenly cards like Necropotence seem rather over powered and abusive. A black deck that aggressively uses its life total and that starts with 15 bonus life sounds dangerous. That said, black is having a pretty hard time of things in the cube at the moment and sees very little play outside of rock and Abzan decks or as a splash for gold cards. With all the various implications seeming to align with the slight balance issues in cube I am intending to try out this change to see if it leads to a better format. If I get enough done like that to give some informed feedback I will let y'all know how we got on.