I sure wish I could be of more help, but there are just so many models just within the Kubota line to pick a "best tractor" for your needs. I have used and looked at quite a few tractors and now primarily use a
L5740 and M8540; both are perfect for our needs/"wants". That having been said, they have all the "bells and whistles" you don't want that I find essential.
The
L3700SU,
L3800,
L4400,
L4600, GL3540-
L5040, MX4700, MX5100 and
M5140 will all do what you want and can be equipped to your specs. Obviously I prefer Kubota, but would recommend looking at all top brands with good dealers in your area; hard to overstate how important a good dealer is.
Loaded tires/wheel weights: For me I prefer fluid, but there is nothing wrong with weights other than cost. We have a tractor with both and I may add weights to my
L5740 if needed; use depends, so modifications can be made later.
4 wheel drive: A must have when working in hills, tried both.
HST: I have driven a couple of pretty old HST's and I personally have no concerns about long term reliability. I drive an HST+ and 12/12 Hydraulic Shuttle Shift and like both though the HST is easier to use. Some prefer one, some prefer the other and still some really like the GST.
New Kubota Engines: I honestly don't know, but I traded this year to get ahead of the Tier IV engines; smart move or stupid, time will tell.
Turbos: I live in farm country and turbos are nothing new, our renters have some older tractors with them and both my primary tractors have them. There again, some people don't like them, some do.
FEL: We have tractors with them and some without, I won't buy another without one.
Remotes: I put three sets on my last tractor as I have Top and Tilt. I consider a hydraulic top link as one of the best things you can do, so I would go with at least one set, preferably two sets.
Sorry, but I just have to address the area of "frills" as you mention long term use/ownership. I am 65 and can't drive any of the tractors I was driving when I was 45 and they are all at another farm being used by other family members and I had to buy new in spite of fully serviceable tractors on hand.
I am certainly no expert, so don't take my opinions too seriously.
If you can pick a tractor with:
1. Just the right horsepower, no more no less.
2. Just the right weight, no more no less.
3. Just the right loader/backhoe performance, no more no less.
4. Just the right tires.
5. Just the right transmission for ALL of your needs.
6. Just the right price, no more; don't worry about the "less" part, won't happen.
7. Just the right size; not too big and not too small, just right.
If you can do all this and more that you aspire to in your tractor selection, you can retire from your present job and become a very successful tractor consultant.