This is not "Data Science" specific, but bootstrapping a client base for a new company with no street cred is done nearly exclusively through networking, e.g. you would start by aggressively asking your contacts for referrals, poaching clients that you've previously worked with, etc.
Also, what you are describing is like opening a mechanical engineering shop and saying "we can invent anything that moves". Consider how well that would go. Specialization is the key, at least in the early stages.
Also, what you are describing is like opening a mechanical engineering shop and saying "we can invent anything that moves". Consider how well that would go. Specialization is the key, at least in the early stages.