My perfect mixes of races for inclusion in a OSR/5e game would include the following:
Human - The standard race that provides a touchstone of reality.
Elves - Leave them open as to being big Nordic/Tolkien elves vs. smaller playful elves.
Dwarfs - Because they are cool.
Halflings - Kind of a standard thanks to Tolkien.
Shifters - Maybe have them be straight up animal hybrids, but the general idea is really good.
Tiefling/Cambion - Human/demon hybrids are just cool.
Aasimar/Nephilim - Human/angle hybrids are also really cool.
Lizardmen/Dragonborn - I'm not a huge lizard fan, but many are. They do provide a great resource for those designing new worlds.
Warforged - This might not work for every fantasy setting, but it's great if you want a steampunk vibe. Though if any would be removed from the core, it would be this one.