You always start Customer Development with a vision and an initial strategy as process inputs, but they can and must evolve along with your business model. The Customer Development methodology is intrinsically the search for a validated and repeatable business model. Trying to develop a sustainable business model without an initial vision or strategy gives you no effective way to generate testable hypotheses or validated learning.
I think you are fundamentally misunderstanding the role of vision and strategy, regardless of whether you're talking about Customer Development or not.
In general, and without resorting to dictionary definitions:
- A vision statement tries to capture where you're going.
- A mission statement captures what you're currently doing.
- A strategy defines what you plan to do and what you will measure to track your progress along the axes of vision and mission.
- A tactical plan (e.g. an implementation plan) describes how you expect to execute your strategy, further the mission, and make progress towards your vision.
The distinctions between vision, mission, strategy, and tactics are somewhat subtle, but they all focus on different-but-overlapping things. You really need all four things in most cases.
The customer development method describes the first of the four steps as:
Customer discovery first captures the founders’ vision and turns it into a series of business model hypotheses. Then it develops a plan to test customer reactions to those hypotheses and turn them into facts.
So, you should already have an initial vision (although it often changes based on validated learning), but you need to continuously refine your strategies, tactics, and product goals along the way. As a rule of thumb, you do this by generating and validating hypotheses about your market, your product, your process, your customer segmentation, et cetera ad nauseum.
As you go through the process, everything and anything about the business may change. This certainly includes the vision and the market strategy, so you can't be wedded to them. However, not having a vision or strategy at all has a technical term: floundering. If you don't like terms that sound like a type of fish, then "wandering around aimlessly in search of a viable business model" is a lot less pithy, but just as accurate.