There might be a use for it; even if the same end can be aquired by eff targeting - say you want true class fighter start with a base THAC0 bonus, but don't want to give that bonus to multiclasses. This file includes multiclasses as well, so you can do that at least.
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Also, THAC0.2da doesn't allow kit-specific differences.
Meh. Given you cannot base this on level, it seems far worse than CLAB....