Interesting discussion.
OP - Have you decided on a Nikon 9000 because it is regarded by many as (one of) the best film scanner or because you truly need (one of) the best in order to complete the work you're doing? I think there have been a lot of good points raised in this thread for your consideration. However, in the end it's your time, money and projects/work flow, so you're in the best position to evaluate and make the decision.
I've had similar discussions with countless people over the years when it comes to buying/building a computer. Some people seemingly always try and do things on the cheap, even if budget is not the key consideration. Often -- but not always -- things don't go quite as planned and they have to expend more resources looking into and procuring another solution. On the other end of the spectrum, many tend to overestimate their needs, sometimes by a significant margin. This is especially true among those who consider themselves "prosumers". I understand why people desire to have "the best", especially when money is not a key consideration (must be nice!). However, clearly not everyone needs "the best" in order to get the job done well. But, if money is no object...
Right now I'm researching film scanners (35mm) myself. With advances in software tools, some of my old and less-than-stellar negatives -- there are more than I care to admit -- might be worth a second look. However, I don't have $3K to drop on a film scanner, mainly because it's just not worth that kind of money to me for what I want to accomplish. YMMV. Besides, I'm building myself a new computer and the (hopefully) soon-to-be-released Ryzen Zen 3 CPU, Nvidia Ampere graphics card w/water cooling, X570 motherboard and 32" 4K monitor all need funding. And yes, I truly will need these components for my, uh, work computer.
If you do end up investing $$$ in an older Nikon scanner, be aware Windows 10 Mainstream support ends October 13, 2020. Windows 10 Extended support ends 5 years after that (October 14, 2025). You might consider purchasing a retail (or OEM, but that license isn't transferrable) copy of Windows 10 before 2025 rolls around, just in case your computer dies. Or worse, you buy a new PC and the new MS OS (Windows 11? Core OS? Polaris? Tik Tok OS?) causes problems. Sometimes, it's better not having to re-invent the wheel (e.g., making things work under a new OS) when you already have a setup that has proven itself.
Good luck in your quest for a Nikon 9000 scanner.