An absolutely superb supplement! I'm a big fan of adding more breadth and depth to 5e's armour and weapon tables, so this document is a great add-on. I run a low-fantasy campaign, so there's nothing in here that messes with even my strict and basic scheme!
The suggestion to have options like the Hot-Blooded Horse and the Warhorse variants as potential upgrades for existing mounts is absolutely great, I wouldn't have thought of that myself! A super simple, super sleek, and super handy addition to any player or DM who fancies adding a bit more diversity and flair to the 5e system without re-inventing the wheel, love it! :D
A quick question for you Scottomir; do you have any suggestions as to the carry weight of your custom mounts? I'm adding a few fantasy mounts of my own and wondered if you had a particular direction in mind, e.g. the Rouncey carries less than the standard Warhorse but with more speed and health, the Charger carries the same and is a flat upgrade, and the Destrier carries more with more health but less speed.
Love and peace!