Look for classic shape...
I think it helps to look for moderate lapels- the big ones look worse when they have less jacket to spread over. Also, a three button jacket tends to have a higher "gorge" or opening, which does better when chopped. You may find the pockets on "hacking" style jackets are placed higher than those on American sack styles, but they still may not sit low enough to avoid moving them. If possible, figure out where the flaps ought to be in relation to some fixed point, such as your chin or your shoulders ( or your wrists) and measure and compare to that point when evaluating.
I still have not figured out if there is any advantage or disadvantage to buying a jacket in the wrong length, i.e., a regular guy buying a long or a short, or a tall guy buying a short or regular. If you can work with the sleeves, you might be able to manage the length and pockets better - or not. Just don't rule out the wrong length if you are going to cut it anyway...
As for color, I vote for something mixy- loden green or heathered blue, though navy is never a bad idea and brown tweeds work fine for day.
"Saxony" might almost be a mock heraldic term, though what it would mean, I can only wonder.