My appaloosa x TB is 16.3 (most swear she is 17H - I only have a weight tape to measure, so maybe she is). Granted, not a “warmblood” -but a tall big bodied horse.
The majority of the riding I do is trail riding. From fire roads to single track, steep and narrow, lots of hills - she does great!
Biggest draw back - I have to duck more under trees etc - they just aren’t pruned to as high as I am up there! No problem though, I just tuck down. I have been known to get my head a wither height and squeeze under branches.
As for getting off and on, there is usually a hillside, rock etc that I can use to my advantage - if not, I lower my stirrup a hole and haul my butt up there.
Saturday we found this big bull lose - had fun herding him back to where he belonged - up and down embankments, squeezing between trees and plowing through brush. I forgot “cow ponies” are usually a big smaller - but I feel I can take my “big” horse, anywhere the littles can go.
Denny Emmerson talks about distance riding their horses - including warmbloods on his FB page. WBs should be able to do 15 miles when fit.