While it may work in a few situations , I think it’s rather ridiculous to think many “failing” golf courses will look at the option of spending millions of dollars as a way to stop failing.
Of course it's unique to all situations, but the state of Georgia did just that with Bobby Jones golf course. After acquiring the old 18 hole course in a land swap they completely rebuild the property as a reversible 9 hole course and driving range. After nearly 2 years of operation under the new model they appear to be doing quite well.
Granted, I believe that Bobby Jones is an outlier in this area and would agree that not many courses would either choose to or be able to fund a complete redesign. Rather I'd imagine struggling courses would look to the success of non-traditional projects such as Bobby Jones, Goat Hill, Winter Park, Sweetens Cove, Schoolhouse 9, etc.... they would see viability in this non-traditional, less than 18 hole championship model, and look to reorganize what they offer to the public. This may open the door to re-utilize some of their land, potentially using it as a new source of capital, and reorganizing the course under a new operational model that allows for greater flexibility and higher utilization.
I understand that every additional acre of green is cheaper to maintain than the previous acre and operational cost for a less than 18 hole course may not be dramatically lower. But value to the modern player seems to be focused more on time and accessibility than cost per hole.
The old definition of what golf 'is' has become more fluid in today's world. While the old guard may keep a staunch view of 18 holes or bust, newer generations are looking for more flexibility and have become adapt at appreciating the game in many forms.
It wasn't that long ago that the number of 9 hole courses in the US outnumbered 18 hole courses. I don't know if we'll get back to that point any time soon, but there does seem to be a growing lean in that direction and further appreciation for multiple acceptable versions of golf.