Hyacinth's Legion
The first Into The Breach mod I have here (dubbed "Hyacinth's Legion") provides a squad of puppets recontextualized as custom mechs.
The first squad added is the Hyacinth's First, which includes the Manipulator, Trickster, and Reconcilant (with Imps starring as deployables). I'd say the squad is on the more powerful side, though it has weaknesses in the form of limited knockback opportunities and a slow start due to needing to spend turns on spawning Imps. There's some fun potential buried in the unusual skills and strategy, however!
The second squad (added in v0.2) is Hyacinth's Analogues, which centers around the Anchorage, its Serfs, and the various Analogues they build and support together. This squad leans even heavier on unit spawning than the Hyacinth's First, with a wide variety of inter-unit interactions including repairs and upgrades. There's a lot to explore with this bunch, though if you're unfamiliar with spawning squads I suggest using the Hyacinth's First, well, first.
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Hyacinth Pilot
The second mod I have is the Hyacinth Pilot mod, which adds Hyacinth as an unlockable pilot. They have custom art, dialogue, and a unique skill that spawns a new puppet type, the Myrmecoph, at the start of each battle. While I attempted to keep a vanilla level of balance with the Hyacinth's Legion mod, the Hyacinth Pilot is quite strong; I recommend using them on higher difficulties.