IMHO, there is a marketing problem and rebuilders need to find a way to address the above questions and not just assume consumers are just buying brands. There is not even one place for consumers to find a list of rebuilders.
Your points are completely valid, stated directly, yet good nature'd in a way that invites polite, informative, non-judgemental give-and-take...I would like to meet you sometime...
When I first got into piano work, not being a technician at that time, the pianos I heard and skills that were apparent at a number of excellent rebuilders studios I spent time in, were so clearly beyond what I was hearing at the showrooms, that there was absolutely no doubt where I needed to be in order to achieve the piano I wanted for myself.
So lets start with "the marketing problem". First, you are absolutely correct, in that it is a marketing problem...marketing in that it is a perception problem, not necessarily an accurate representation of the reality.
Marketing in sales, especially high-ticket items, is absolutely essential to generating sales. There are both positive and negative aspects to this. We have all become somewhat cynical on many of the aspects of marketing, and our defenses have to be up at all times...buyer beware, and rightfully so. This is the negative side, where we all have to know whether and how an entitiy is manipulating or trying to manipulate our emotions. On the positive side, marketing, when it presents honest information, forms viable and sincere trust relationships, and avoids pushing hot consumer buttons can really help a consumer find their perfect fit in a way that the consumer, on their own, might not have been able to pull off.
As you say, consumers are not experts in everything. We can't be, as there is too much to know. Thus, the scope of how educated one can be in making a high-ticket purchase decision can be, and often is overwhelming.
However that does not leave the consumer up the creek without a paddle by a long shot. There are at least 2 ways that consumers are complete experts in the piano field. 1- they, as human beings, as a matter of survival, are expert at evaluating whether a relationship can be trusted, and 2- serious piano consumers have an inner muse who is their guiding star in their quest. The muse must be acknowledged, listened to, trusted and empowered throughout the entire process. In both of these fields of expertise, forming "trust" is the essential and unavoidable component to making a decision that will be happy one...one forms trust in a person-to-person relationship, and the other forms trust in the authority of one's inner muse.
The ability to find a person where trust can be sensed, evaluated, tested, and ultimately relied upon, both in the short and long term, is one's ticket to finding the piano that will ring your bells. The trick is to realize how strong the emotional side of any piano decision is, and be vigilant enough to see if one is being manipulated or empowered.
As you speak to anyone regarding your decision/quest, whether it is a brand representative or an individual artisan, do you feel empowered or do you sense your emotions are being manipulated...this is the bottom line. One's muse knows darn well whether its voice has been trusted or negated within the confines of the sales relationship.
So my answer to your question of "how does one know a rebuilder has the chops" (my paraphrase) is two fold. Listen to and play either the offerings or previous re-manufactures. Listen to and respect the experise of your muse regarding the sounds and touch. At the same time invoke your relational expertise...you know when you are being empowered and when you are being manipulated.
This is probably not as binary an answer as you would have liked when you asked the "hows" of how do consumers decide whether a rebuilder or I would say any sales entity, is to be trusted. But there is no escaping it; trust is the
essential ingredient in all human relationship, and purchasing and honing any piano requires developing a relationship. All of my clients with serious interest in their pianos become friends as well as clients... we share a mutual emotional connection to our pianos, and we have shared the challenge and up-and-downs of the quest.
Every sales entity, be it a branded piano, showroom, or individual knows that developing trust is essential to convincing consumers to make a high-ticket purchase. Each entity develpos a strategy to elicit that trust. Brands often invoke the celebrity connection, the institutional connection, the status connection, the tribal connection to elicit that trust. Even though they may offer excellent pianos, they don't rely on empowering one's muse to develop the trust relationship, but rather they develop the relationship by proxy.
Small high-end one-on-one rebuilders are individuals and develop the trust directly, person-to-person rather than by proxy.
There is more to this in the specific technical side, but lets start here, and let the give-and-take reveal more.