Beware of step 2 to step 3. I call it "chasing the whale". The problem is the "whale company" knows they are a whale. You'll slowly watch your entire development timeline and features shift to benefit only them. Your company basically becomes a contractor for them to get X feature working (and nobody sees this feature being helpful to any other customer). You can't get rid of them because it looks terrible for funding that you dumped such big potential. Technical debt piles up from priority shift and then the whale is gone. You were only a POC for them, and in the wake of being side lined as a priority other customers leave.
I've seen this happen multiple times.