Ok, the biggest challenge of this cube is going to be that colors are just not as good as each other at aggro, control and midrange. A more natural arrangement would be something like:
Aggro
Aggro-control
Midrange
{W/R} Control
Fortunately, I'm not playing chaos drafts, and this is cube, so I pick which cards I include. The goal is to run similar densities of cards in all colors appropriate and specific to those archetypes, at similar power levels, and get as close to the goal as possible - though recognizing that some colors might still be better than others at certain macroarchetypes. We can fortunately get some help from the self-correcting nature of draft to smooth out these imbalances. Still, I'll make an effort to have macro archetypes be as balanced between colors as much as can reasonably be done.
There are lots of challenges, so let's work through them. Fortunately, this was the design of the Elegant Cube for years, so I actually have a good idea of what I'm dealing with!
Challenge: Control is blue
Why is control almost always blue? Because of counterspells and good card draw.
Counterspells are the only things* that can interacts with sorceries. Artifact removal and counterspells are the only things that can deal with artifacts. Same for enchantments. Counterspells are even good against planeswalkers - though burn, and attacking creatures can also interact with those.
* discard can interact with all of those actually, but it's not reliable in long games because a topdecked card has no window to be discarded.
No other color has the versatility to answer threats that blue has, though white comes fairly close with is
Oblivion Rings. Also, no other color has a meaningful amount of counterspells.
Card draw is another area where blue is significantly above the rest. Control's plan is to build card advantage while not dying, and to build card advantage, nothing is as consistently effective as drawing cards is. Black has card draw too, but often worse and tied to loss of life. Red's card draw doesn't allow it to accumulate resources usually, using the exile card draw of
Light Up the Stage. Green has card draw but often tied to having creatures.
How do we overcome the fact that blue is the best control color?
Well first, let's recognize that it will likely still be the top control color if I'm running anything resembling typical blue. With that out of the way, let's mitigate the imbalance between blue and other colors!
Because blue aggro-control will be heavily supported, the blue card pool will not be all usable by control. This scarcity in blue control cards should prevent blue from being drafted too many people in the same pod. Running a significant amount of cards aligned solely with aggro-control and not with control, like
Force Spikes, is necessary to create this scarcity.
Card draw is a powerful way to create a strong endgame, but card draw scales well to power level, and other colors can match this card advantage at a lower power level if they are provided with tools to create this advantage over time with a similar profile. Note that if these CA-positive cards are tempo-neutral or even tempo-positive, they are more like midrange cards than control. True analogues of card draw should be tempo-negative. This will cause me to run some pretty particular cards that can perform this role.
Of course this introduces the constraint that the environment has to be slow enough that these are playable.
Colorless card draw like
Cosmos Elixir and
Sunset Pyramid can also replace blue card draw in non-blue control.
To add to card advantage in other colors, we can use effects that create card advantage by being more card negative to the opponent than a 1-for-1. Notably, wraths are good at this while not letting you get ahead yourself, preserving them as control tools and not midrange. We can also use other defensive 0r neutral 2-for-1s.
Ok, we have given other colors options to match blue's card draw. What about the fact that counterspells are clean answers to everything?
To start, we should be careful with permanents that have valuable ETB effects, particularly effective ones against control. The reason is that removal is much worse than counterspells against them, so we make removal better relatively to counterspells by limiting our
Cloudblazers. Note that ETBs that are not good against control like
Flametongue Kavu or
Lone Misisonary aren't much a problem for this, and their inclusion actually makes counterspells better than removal in aggro/aggro-control decks, effectively buffing blue aggro and making it draw more generic cards from control!
Then, we must make sure combinations of colors are versatile enough to have answers to threats. Non-ETB creatures are ok because they can be dealt with with removal and wraths. We're more concerned with artifacts, enchantments, sorceries (instants too I guess?) and planeswalkers.
White and green have tools to deal with artifacts and enchantments. Red can deal with artifacts and planeswalkers. Black can deal with planeswalkers and use discard somewhat. We need maindeckable effects in these categories that control can run, and versatility really is key to make them maindeckable.