This took a little bit longer than expected, since it required certain updates to the base stdlib mod, which I was finally able to release (I don't like making minor updates to core mods). The nickname functionality works basically as described, as an optional addition to the beginning of the loadout string
If it's not included on any particular row, that row will use the basic numbered loadout instead. The default mod setting for the first customizable loadout should showcase this functionality as:
basic: smg smg tank tank
Note: The first mod setting is exclusively an optional nickname setting for the original Spidertron loadout, which was customized in the original mod (and does not use the customizable interface that the rest of the squads use)