not for less than the cost of a new board. not at scale.

a small shop can do it if they grow slowly. a component-level repair shop run by Microsoft which did not swap parts, but repaired them, can not scale quickly. there just isn't that much talent available to do this, and even when there is, it would be tight, economically.

it costs Microsoft less to build a main board than the price they sell it for. the hourly time of the repair person multiplied by the time to diagnose, repair, test, document, and clean a main board would quickly go beyond what a new one costs Microsoft.

component-level repair just is not feasible at scale.

should they make schematics available anyway? yes.