For years in manufacturing when a company was well-capitalized they produced parts that had a high-turn rate and sold them to their dealers to stock, taking the burden off of the manufacturer to carry 100% of the inventory and spreading that inventory through the dealer network. To be a dealer, or in this case an MSC, you had to stock parts.
Once the machines in Kerrville are set up to produce a certain part number you can get some economy of scale by producing enough of that part to get your cost per unit down. Then if they could load up the supply chain to the dealers that would help take care of cash flow to keep the overhead paid. In my opinion, the MSCs should be the ones investing in Mooney. If they believe in the future of this, as an example, if 10 of the bigger MSCs put in $10,000-$15,000 each to get the ball rolling, to me that would make a lot more sense than individual owners who don't even need a part at the moment putting money on deposit. Smaller MSCs could put in a lesser amount but wouldn't get as favorable of a price structure. It wouldn't kill an MSC to keep some often-sold parts in stock. As @Schllc mentioned, start with the most often requested part and go down the list and build up the supply chain and sell it off to the dealers to stock. The risk for the investment goes down to nothing once the MSC has the parts they've paid for in stock.
Mooney isn't alone in the supply chain being broken. Every shop now servicing any make, is used to ordering every part that they need once they know they need it. By not stocking parts dealers pay an atrocious price per part, and pass that and the shipping cost on each part on to the consumer, all contributing to make General Aviation very expensive for the average person, all while the airplane sits there waiting on parts clogging up the maintenance chain.