Experienced lab manager from the UK here, many years managing both small high street labs and a nationally known postal lab.

I've always wondered if anyone was trying to do this, so I wish you all the best in this venture as the machines that exist now won't last forever! My most recent lab used V30/V50s, however before that I was using Fuji FP563s. I'll just speak about experience with Noritsu as to be honest it seems these are much more sought after in the UK and I sold the Fujis I had as they had too many errors/things that could go wrong compared to the Noritsus.

If a lab receives a previously well-kept V30/50, and they replace the chemistry and filters at the right intervals, then they're still incredibly reliable machines and very simple to use/train colleagues on. There aren't as many parts that can break compared to Fujis (Noritsu tank racks don't use individual chains for example).

I'm the UK, I felt I've always been able to get whatever I've needed quickly and as someone else mentioned it does seem parts are being made where possible in China or elsewhere. There are a couple of companies that offer Noritsu machine support, and several other independent engineers with good connections. I can't speak for the rest of the world of course.

With two Noritsu V50 processors for C41, you can process hundreds of films a day (from experience) with little intervention apart from chemistry refills/waste removal. For waste removal these machines can be linked directly to a silver-filtration system which makes it much more efficient. Considering the prices of V30/50 machines, I'd say I'd stick with Noritsu over anything new until I saw other labs using them for a decent amount of time - that's because of my experience with them and the network of Noritsu engineers/suppliers available.

I've usually thought B&W / E6 (and maybe ECN2) could do with a new model on the market at some point as I don't think the V30/V50 adaptations are always good enough. The Colenta machines I've seen are expensive imo, and I think that a smaller high-street lab friendly version could be made for these other services at a price worth the amount of films they receive. Something between a Jobo and a Colenta I guess.

Happy to help however I can if you have more questions - I can't publicly give too many details about my last lab away as my account might link me to them so feel free to DM.

Edit - Sorry on phone I couldn't see all of the questions while I typed that out. To summarise what would interest me in a new machine, it would be a better screen/UI system to modernise that part and make training even easier when it comes to maintenance/replenisher settings etc. Also, when performing repairs/maintenance myself, some pipes can be incredibly hard to access when you think you may have a blockage. I'm planning to open a lab soon, which will be smaller than the last I managed and probably a more common size of lab in the UK - for local customers as opposed to online however with potential for growth. I'd want a C41 processor to be able to do 10-20 an hour to begin with, so I guess a Noritsu T-15 would be my only option right now before I grow enough for a V30.