Are you talking, that someone can actually make stats of weapon better? No! Only server can do that, and then it apply to all such weapon users...
I will show you what can client:
Client - contains textures, models etc + single player data, so all scripts etc. If client will make weapon stronger, it will apply only to singleplayer, untill server will do that, too.
Server - doesnt contain any textures or modelts etc, but contains all scripts needed to run game. Script files (.txt) in server module override client scripts, until it is compatibile with client scripts. If it isnt, client cant get to server or client/server get crushed.
So noone can cheat with +20 weapon lenght etc until server host will do that.
If you are talking about reticule, then yes, you can of course stick some "real" reticule to middle of your screen. And what then? it DONT give you real accuracy, because it WONT change (while adjusting to your bow accuracy).
No advantage. And it is really easy to get reticule in Vikingr back. I repeat that!