The thing with having a heavy concentration of
Vivids and
Pools is that it encourages you to play all five colours - why stop at three?
A lot of our cubes on here already encourage and reward three-colour decks, what with their heavy density of fetchs, duals, and shocks. To be sure, the decks that tend to do well in my draft are often three colours; the mono and two colour decks suffer for not being greedy enough, which is something that I'm still learning to absorb, as it goes against the lessons ingrained in us from playing retail limited. It would probably only take an additional cycle of dual lands to encourage the majority of our playgroups' drafters to go three-colour, rather than having a number of people play it safe and stick to two-colour.
The thing is, though, playing a three-colour deck still doesn't encourage people to draft three-colour cards. I might end up going BUG, but am I really taking
Sultai Charm P1P4, when I can safely take the mono-blue or mono-black card and keep my options open early? I sometimes find that I think I've drafted one particular colour combination - say, Bant - but when I take a look at my card pool, it turns out that my blue is weaker than my black, and I'm actually Junk. Taking a
Bant Charm in the middle of pack two would have been worse in that situation than almost any other mono-colour, or even two-colour, option.
My completely untested theory is that you need to reward players for taking narrower gold cards by establishing a hierarchy of power: weak mono-colour, stronger two-colour, very strong three-colour. This would let people have a payoff for taking risks mid-draft, as opposed to the usual strategy of trying to stay open as long as possible. I don't know whether this hierarchy would lead to good draft dynamics, as this itself is poison principle in a way. But I think getting a drafter of yours to cast
Jeskai Charm will take more drastic measures than tossing in some tri-lands, and this is one idea.