What you think your institution needs at the outset of a tech project is very rarely an exact match to what you realize your institution needs by the end of the project. That’s just a fact of life in the digital age. However, there’s a fuzzy line between tweaking things to make sure they’re right and insisting on everything plus the kitchen sink.
Keep a firm grasp on the difference between “must have” and “nice to have,” the difference between “need it at launch” and “need it in six months.” Most important of all, engage your vendor in constant, productive dialog. Remember, your vendor wants exactly what you want, namely a successful implementation that everyone can be proud of.