Replacing default weapon with attachment

[Foxace]

How to replace for an example melee paladin hero's hammer with custom attachment? I tried giving attachment to paladin but the original hammer remains with model.

 

[Dr Super Good]

I tried giving attachment to paladin but the original hammer remains with model.

That is because the hammer is part of the model.

How to replace for an example melee paladin hero's hammer with custom attachment?

Use a custom paladin model where the hammer is removed. You can then attach any hammer to it, even a default hammer, as long as you have the hammer models you want to use.

It is important that all of them have correct attachment points otherwise the results may look ugly (hammer inside his arm as an example if the hammer has the wrong attachment for origin).