Yooper,
Re seat/control positioning -- I would encourage you to keep in mind movement and repositioning of the tractor/cutter wheel. With my small tractor I have to constantly reposition the cutter and this is one of the great benefits of having the HST drive - my sitting in the seat turned to the rear, with little movement of my body I can not only control the cutter position with my left hand, I can also raise/lower the 3pt, and with right foot press the reverse pedal and with left foot press the fwd pedal. This means that I only have to change position when needed to drive the tractor - this is a tremendous feature when I have to reposition the cutter.
I'm not familiar with your tractor - HST or shift? With a shift tranny you are gonna have to change seat positions to reach clutch and shifter. While a swivel seat sounds like a possibility it may present to much of a hassle to change positions. I'm thinking you might oughta try the conventional seat with you turned to the right for starters ... Course then you have to go back to where you position the controls? -- maybe rig a temporary mount for them? I've got a handful of zip ties in that mount on mine! Saw a couple rigs where the guy mounted them to the right side of the ROPS bar - could probably zip tie them there temporally for a test position.
Even if your tractor will eat more off a stump than mine, I think you will be surprised how often you have to reposition.
Course what kind of tree you are working on also - and state of rot or not will be a huge factor in all this. The 80-90 of mine are all pine cut about a year and a half ago so rot is beginning but not real beneficial. The old large pines also have a tendency to build a 'mound' of dirt around the base in which roots - some large - to run in them needing more time to find them and "root" them out
You've got the right idea about letting these problems "percolate" in the back of your mind as you go about tending to the other builds ...