I am glad I happened to look back at this forum... I may be able to help you.
I hope you mean editing weapons on a map, not for the whole game. I don't know how to edit .lvl files or any of that.
To change a units weapons, and then to edit the fire rate/power/color/anything of the weapon, you'll need to "create a side" for your map in BFBuilder. Each unit you want to change will have to be in this. From the Assets folder, grab the .odf file for the unit you want and copy it into your sides ODF folder. Likewise but the units meshes, textures into the MSH folder. Open up the .odf file for the unit you are editing for your map (after unchecking "Read-only" in the properties of the file, so you can save your changes). Here is something like what you want to find in the .odf--
WeaponName1 = "rep_weap_inf_arccaster"
WeaponAmmo1 = 0
WeaponName2 = "rep_weap_inf_pistol"
WeaponAmmo2 = 0
WeaponName3 = "rep_weap_inf_thermaldetonator"
WeaponAmmo3 = 3
WeaponChannel3 = 1
WeaponName4 = "rep_weap_inf_powerup_dispenser"
WeaponAmmo4 = 5
WeaponChannel4 = 1
Switch out any of those with any "rep" weapons (using a side's weapons that won't be in your map isn't this easy).
For example, if I want to replace this unit's health dispenser with some mines, I replace
WeaponName4 = "rep_weap_inf_powerup_dispenser"
WeaponAmmo4 = 5
WeaponChannel4 = 1
with this from the arc_trooper .odf file-
WeaponName4 = "rep_weap_inf_mine_dispenser"
WeaponAmmo4 = 4
WeaponChannel4 = 1
Hope that is enought to get you started. Editing weapons requires copying the desired .odf to your sides file, as well as the .msh and .tga, and calling for the weapons .odf in the unit's .odf code, such as:
WeaponName1 = "rep_weap_inf_shotgun"
WeaponAmmo1 = 7
Before you can mundge this and play it, you'll need to edit the sides .REQ files to reference your new units, and then edit your mission .LUA file to call for the new units.
As usual, you'll get more help at gametoast (
http://www.gametoast.com).