Changing models used to be possible here (even changing to Luclin models
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Then some guild used that trick to change NPC models. I forget if it was to see whether an NPC was carrying certain loot (that you couldn't normally see visibly), or if it was to make a boss mob easier to click on (for racing) ... I think it was the latter ... but anyhow, since then the staff disabled model changing.
As a result, without some serious (ban-worthy) hacks, I don't think changing your dagger into a sword is possible on P99.