This is an ultimately fairly simple mod that lets X-COM research how to create Alien-Human hybrids and then recruit them for use as soldiers. In order to get them you'll need to research Psi-Labs, Alien Reproduction (which means you'll need a mod that makes that obtainable), and a Sectoid Corpse (mostly for flavor).
Hybrids have slightly lower stats in most ways (lower starting stats and lower caps), but have much higher psionic potential and come with a built in psi-panic attack, the same way mind controlled aliens do. They also have a custom set of names, so they'll show up being called things like "Subject Delta" or "Experiment 003". Once you've unlocked them you'll also be able to research and manufacture a personal armor equivalent for them, and a slightly worse version of power armor for them.
I made this mod mostly for myself, but I decided to release it partially because Solarius Scorch asked if I would and partially because I don't think there are any other mods that add new soldier types quite like this available and if nothing else it shows how it's done pretty clearly.
Credit goes to Solarius Scorch for the Hybrid sprites I used for unarmored hybrids, and XOps's Xeno Operations mod for the sprites I used for armored ones, shadics for the sprites for motorized armor, and Zane for the motorized armor inventory sprite.