[Exolent[jNr]]

new gVault;

public plugin_init() {
    gVault = nvault_open("weapon_models");
}

public plugin_end() {
    nvault_close(gVault);
}

SaveModels(id, weaponID, v_model[], p_model[]) {
    new steamID[35], weaponName[21], key[64];
    get_user_authid(id, steamID, charsmax(steamID));
    get_weaponname(weaponID, weaponName, charsmax(weaponName));
    
    formatex(key, charsmax(key), "%s-%s-v", steamID, weaponName);
    nvault_set(gVault, key, v_model);
    
    formatex(key, charsmax(key), "%s-%s-p", steamID, weaponName);
    nvault_set(gVault, key, p_model);
}

GetModels(id, weaponID, v_model[], v_model_len, p_model[], p_model_len) {
    new steamID[35], weaponName[21], key[64];
    get_user_authid(id, steamID, charsmax(steamID));
    get_weaponname(weaponID, weaponName, charsmax(weaponName));
    
    formatex(key, charsmax(key), "%s-%s-v", steamID, weaponName);
    nvault_get(gVault, key, v_model, v_model_len);
    
    formatex(key, charsmax(key), "%s-%s-p", steamID, weaponName);
    nvault_get(gVault, key, p_model, p_model_len);
}

// to save a new knife model for a player
SaveModels(id, CSW_KNIFE, "models/new/v_knife.mdl", "models/new/p_knife.mdl");

// to get models player is using
new v_model[64], p_model[64];
GetModels(id, CSW_KNIFE, v_model, charsmax(v_model), p_model, charsmax(p_model));

if(v_model[0]) {
    // set view model
}
if(p_model[0]) {
    // set weapon model
}

Hook Ham_Item_Deploy as a post hook and set the model there.