I knew someone would make this xD
Not able to pick up the gift. It doesn't disappear. //EDIT - just realized that my ammo was full when testing, if you can pick up more ammo it works.
You can use
SetEntPropEnt(client, Prop_Data, "m_hObserverTarget", client);
SetEntProp(client, Prop_Data, "m_iObserverMode", 1);
to enable third person
SetEntProp(client, Prop_Send, "m_iObserverMode", 0);
to disable it.
you should also use TF2_AddCondition and TF2_RemoveCondition to manage those conditions.