You already named the main problem, the weight of any battery sized sufficiently for years of trouble-free usage. Also, excepting the big boys over 75cc, most are too easy to pull over to make that any primary obstacle for most new saw buyers. A lot of 75+ year old members here may own and use chainsaws, but their new saw buying days were probably 10+ years prior, so their unique challenges don't get figured into the manufacturer's design decisions.
Running it off the tractor would be pretty slick, for those who only use their saw near a tractor. You'd have to overcome the current limit of a cigarette lighter jack, usually 20A, but that could be handled with a DC/DC converter charging some big on-board capacitors, with a few seconds of charging before green-lighting for a start. 12V capacitors are not heavy, and the DC/DC converter is almost weightless.
I think it'd be a niche market item, maybe the sales forecast is just too low to justify the costs involved. Of course it's a compound problem, low sales projection leads to higher manufacturing cost per unit, on top of the already-fixed NRE costs.
I do have one saw that's a very hard pull, at 85cc with no decomp valve. I've given a few cutting partners the chance to use it, and they've all handed it back after one pull attempt. You need to yank the cord like you want to hurt the thing, but it always starts after just 1 - 3 pulls.
My saws with decomp always seem to take more pulls to self-prime with the decomp pressed, versus without, so I actually almost never bother pressing the button.
