There is an old parable [from Earl Nightingale] about a man is sitting in front of a cold, empty fireplace and demanding, “Give me heat!” Obviously, you must first put fuel in the hearth and light a fire before you can expect to get any warmth.
The same holds true for OctopOSS projects. You only get out what you put in. Customers need to be deeply involved in a project for so many reasons. Don’t just throw the hand grenade over the fence and expect the vendor to catch it and defuse it, delivering a perfect OctopOSS at the end.
Having been involved in a wide array of consultancies over the last dozen years, it is clear to me that the best outcomes have arisen from briefs where the customer was most deeply engaged. The converse has also been clearly apparent.
So if you want to your OSS to be a perfect-fit for your unique needs, get your hands dirty, get involved in specification, data gathering, data migration, environment building, testing, training development, application configuration, process design, training, change management, etc, etc.