Here are my initial thoughts.
Keep in mind that I believe providence and local ministry context are the primary factors in determining the scope of a ministry's vision. This list focuses on developmental aspects of leadership.
#1 The size of your God
This isn't a spiritual throw-in to get the list rolling. This is a very discernible feature in a leader's life. Some leaders have a more cultivated inner life and deeper awareness of God's Word. Their ability to dream big comes from the big God that they walk with and serve each day.
#2 Exposure to others who "think big"
Did you ever notice why many prominent leaders have children who are prominent leaders? I think of Andy Stanley or Franklin Graham, for example. When you are around others with a larger perspective, it rubs off. I am surprised sometimes how leaders tend to stay in a very confined space—geographically and relationally—for their entire lives.
#3 An active imagination
Some people have a tenacious impulse to learn, ask questions and grow how they think. That kind of curious drive pays off. The imagination is your most powerful human ability. Do you exercise it much? Einstein said that imagination is more important than knowledge.
#4 Sequences of risk taking
I'm not talking about a bias for risk in general, but the ability to "stack risk-taking" and feel the momentum of one "leap of faith" after another. Many leaders take a risk or two and settle for the really good outcomes rather than continuing to find even more extraordinary results.
#5 Ability to focus gifting
Most leaders know themselves but don't have a fine-tuned understanding of precisely why God put them on earth. When you do, and when you focus that gifting, big things will result. The scope of your vision grows as your focus narrows. Are you trying to do five things with your life or one thing? (If you want more info on my first personal vision cohort—starting in August— let me know.)
#6 Team and network building ability
We all know wild dreamers who didn't have a team. Your team building ability will dramatically enable of disable the size of your vision. In addition, I am amazed by the increase of wisdom, access, ideas, and opportunities that come through active network cultivation. Wouldn't you expect the vision of a pastor who networks to be bigger than one who doesn't bother?
#7 A goal oriented outlook daily
Every person who achieves a big vision has a basic recipe for attacking the 24-hour unit of time we all possess. What is yours? I have a three kinds of days in my life (focused, buffer and free). On buffer days I determine the 2 most important things to accomplish by 11:00am.
#8 Margin to write down your dreams
At first I wanted to say "disciple to write down your dreams." But discipline is over-rated in this way. The bigger challenge is margin. People enjoy dreaming and writing down their "wish list" when given the time. That doesn't take discipline— its one of the most exciting things you can do! Over and over again, you will see the common thread of big visionaries: Put it on paper
#9 Recovery from big failures
Don't underestimate the power of a good failure. Failures remind you that life is short. Failures expand your pain threshold. Failures purify and humble and bring powerful perspective. Sometimes a failure in one area or with one dream can increase the size of another.
#10 Graciousness and kindness to others
I suspect there are people who excel at the first nine factors but in the end, they just aren't that nice. They don't care about others. They don't stay connected to their teams and their friends. They are so driven, they loose the human element in everything they do. So you might not think something this simple would make the "big vision" list. But I can't shake it.