Let's liven up the topic a bit. After all, this concept can be used not only to create champions for Necropolis. For example, you could place paladins or other human warriors on red armored dragons. They would look great in a human faction. Or you could have riders on griffons. And for the elves, you could create riders on unicorns (both archers, swordsmen, and spearmen). You could base them on the models of elf heroes without the deer skins.
It would add a lot of variety to the game.