Animating a combined skeleton with variable limb sizes

So, i’ve created a character creation system for a mech game.
How it works is that through some data tables and structs, a component assigns a model to the legs, chest, head and each arm, each mesh is attached to each-other VIA sockets (chest to legs, everything else to chest, weapons in each respective place), and then a big messy material is slapped onto all of it and it gets its colours assigned to it.

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However, now I’m a little stumped as to how I’m supposed to animate all of this.
From what I understand, a leader pose might be my best option, but every tutorial I’ve seen involving it is working with skeletal meshes that have the exact same proportions.
So I’m not entirely sure how I should go about this.

Does anyone have experience with animating a custom character that can have multiple limb sizes depending on what parts are selected?