I will simply say that the contracts are an area that most of us may not have realized need more work and must have many more conditions and caveats to protect the buyer.
Otherwise, there may be no schedule for finishing, no expectations of fit, finish even source of parts whether used or new or even refurb.
You, we, are putting a lot of trust in what the usual build is or isn't
Also, what happens if after the delivery date you start chasing an issue who's cost is it and for how long? What if the vehicle develops something that you chase and after 2 years you realize was a major error was a logic error by the builder which caused you to chase it for 2 years at your cost.
These are all potential situations that a custom build can create.
Did I mention, Shipping of the vehicle and the list goes on.
Sometimes I think we as a group should develop a basic contract to detail what a build contract should have after all having a full discussion of all points gives you the best possibility to have a good build and a good working relationship.