*UPDATE*
Just recived an email from Serellan about the NATO 3.5 Weapon Mod. Here is what he has to say:

Work is almost complete on NATO 3.5, we think you will be impressed with the changes. Almost every single bitmap(including the original UO Weapons) has been redone, several new weapons have been added, modelshave been tweaked or redone, and the gameplay mechanics have been tweaked