It would be visually interesting and fun if units grew in size when vetting.
Veterancy shown as unit size GROWTH
I've coded a mod for something similar. There's an issue you run into that you can't replace the bones of a unit on the fly. This gives you two options:
A. Don't update the bones at all, which means GCs will start firing out of their neck and then chest as they grow, and units will get sucked below the arms for some reason.
B. Replace the unit completely with new bones every time it vets, which will reset any targeting and movement it has and will likely be super janky for all sorts of reasons.
Both of these options assume there's a workaround for the 6 uniformscale values we would need for all combat units.
Or what if units got smaller as their HP gets reduced...?
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Rule #1 of FAF : Kill the ACU nothing else matters...