As long as the fan is in good enough shape not to fly off while in use, and to do its cooling job, there shouldn't be any harm in keeping it. You could always just balance your armature if the fan has lost sufficient material to unbalance it. Though I doubt the weight of the fan really compares to the weight of the armature.
You could buy a Dubro balancer, and you might have to make a piece of wood to mount it on, like I did. Stick the armature on it, see if it has a heavy side, and either add or remove weight to one side to balance it out. Pretty simple, really.
[URL unfurl="true"]https://www.ebay.com/itm/NEW-DuBro-Tru-Spin-Prop-Propeller-Balancer-for-Air-Heli-499-FREE-SHIPPING/190867035161?hash=item2c708fd419:g:eXIAAOSwB5tbOSAx[/URL]
