Another principle might be "Complies with accepted standards". Examples would be the ASAE (now ASABE) 3 point hitch and quick-attaching coupler standards S217.12 and S278.6 and SAE universal attachment standard J2513, mentioned elsewhere in the forums.
I think the tool that best personifies these principles is the 3 point hitch toolbar. We have set up a number of toolbars, using a wide variety of purpose built and adapted tools.
I like some of the ideas you both wrote. I love the Farmall Super C and Super A, both great cultivating tractors with position control on the midmounted implements, On the C with an auxiliary valve controlling the fast hitch, the depth of the midmounted cultivator gangs could be indepently adjusted on each side. There are PTOs for operating sprayer pumps while cultivating and for operating midmount implements like planters and sidedressers timed to the drive wheel speed, a great, extremely durable and readily repairable engine, and tremendous crop visibility, relatively easy to steer, and built to last. What I don't like are the difficulty of climbing up onto the seat, the lack of power steering, (I have bum knees and don't have the arm strength I once had) the inability to reduce speed adequately for delicate cultivation without clutching, and the gas motors that require constant tuneups, carburetor work, and the unavailability of suitable fuel. The play in the steering is another weakness.
The features I would like are power steering, comfortable seating and access to the operator platform, and a diesel engine.
We need a lot of ground clearance. 24 to26 inches would be enough to clear our tall raised beds and get over the crop. We used to use the A and C for all the cultivating, but they are too short, and in the case of the A, too narrow to get over our beds.
We have standardized with 72" or as close as we can get to that for wheel centers. Our beds tend to end up at 72" to 76" on center.
In the best of all possible worlds, front, mid and rear mounts.
For us old folks hydraulics are a must. An absolute necessity for heavier implements.
PTO for a sprayer pump is an absolute must. Auxiliary hydraulics are handy, they could be an option.
The 23 HP motor on the farmalls was plenty of power for their size, but relative to modern motors, their 123 cu in displacement and heavy flywheels made for lots of inertia and ability to pull through tough spots. Also, if you go to hydraulic drive, you will need more HP to make up for the lost efficiency.
The ability to perform multiple tasks is pretty important. We can cultivate with front and rear implements, spray and sidedress at the same time with out NH TD95 HC tractor. I used to do the same with the A and C with midmounted and rear mounted implements. The problem with our HC tractor is you can't see the crop the way you can on the A and C. The other need is for slow ground speeds for delicate cultivating and waterwheel transplanting. Four wheel drive would be nice, it helps a lot to reduce side slippage on side hills, but I'd rather have a tight turning radius for maneuvering on headlands. Two wheel drive tractors require large diameter drive wheels to pull through wet spots and push front and mid mounted implements. The C will get through spots that stop our 50 HP 2WD JD utility tractor dead. There needs to be adequate lift height to raise midmounted implements over tall beds. Depth control for hydraulic lifts would be nice. Standard Cat 1 hitch dimensions are important. I am converting the C from fast hitch to 3 point hitch to gain some ground clearance and I will use combo Cat I and II balls and make sure that the hitch will go narrow or wide to accommodate both standards. We use Cat II quick hitches on both our main tractors to make changing implements easier, faster and SAFER. The front hitch on the large tractor has Walterscheide ends on the arms. That system, too makes changing implements a snap. Good brakes are an important consideration, including an easy and reliable parking brake.
I like the idea of toothed or ribbed timing or gear belts for final drives. During my 19 years as a plant engineer in a textile company we used timing belts to replace chains and v-belts on lots of drives, including some 15 and 20 hp drives. They require far less tension than v-belts, have far less lash than chains, and time drives impeccably. Plus they run cooler, longer, and quieter than the others, they stretch less, and they don't require lubrication. The only time I ever had to replace a belt was when a mechanic grossly misaligned a motor. By incorporating a speed reduction in the final belt drive a lighter transaxle could be used.
Finally, a hybrid diesel electric drive system and a fabricated chassis would be great.
I, too, am delighted to serve up my wish list. Please continue posting your thoughts.
Our shop has a welder, drill press, pedestal grinder, chop saw, hand grinders, oxyacetylene torches, die grinders, and hand tools. We repair and fabricate a lot of equipment with these simple tools. The chop saw and hand grinders with the thin cutting wheels are great metal cutting tools. We rarely use the torches for cutting metal anymore. A welding table is a great addition to the shop. We just use a 24"x36"x3/8" piece of plate laid on a pair of horses. It allows us to set up jigs with a few clamps and scrap steel, and set up work without a ground clamp.