What prevents a 100 mm BT from offering a relatively larger true FOV, say 6° to 8.5° that a pair of 8 x 42 mm binoculars provides?
Or it could provide larger true FOV but would suffer from some other issues that I’m missing?
It is possible, but even well-funded astronomers don't reach that high.
Film producers, sometimes.
Aside from eyepiece issues, the abberation of the short barrel becomes severe,
incurable by just 2-3 ED elements..
Looking at cinematic lenses, you could reach down to ~F2.8, but the 100mm telescope would
require 5-7 elements and the price (for the same transmission and quality) would
rise to maybe 30-60K$. Your eyepiece issues would be partly alleviated, though.
It's doable, but for a very high price. And you may need
a fine sensor do do what your eye cannot.
Given the same amount of money, astronomers would be
reaching for power and distance instead.