You don't have to install anything else, just edit the script file of TooManyWeapons.
It's done by adding admins' USGNs into a the adminList table at line 210 (line number as of writing this, please use text search)

If you use [ADMN, DEV] Permissions - WIP (13), there are two types of permissions:

and there're per-weapon permissions:
As you see, it's all lower case & spaces are replaced with underscore "_". You can find the internal weapon names inside the script in the huge list at line ~100

You have to add each permission node to be able to equip any item. Once Permissions supports the following feature, it'll be enough to add "toomanyweapons.weapon.*", which is not the case at the moment. I know, it's a nuissance, but it gives you 100% control on what your admins/moderators can equip.

v1.3b:
typo in the function that is responsible for equipping bugged aka unequippable items

v1.3a:
An unintended script bug which required [DEV] Improved print() 1.1 (8) to be installed

v1.3:
You can now equip other players: !TMW [id] (as suggested by Mora)
Permission node "toomanyweapons.equipother" - allows equipping other players
TMW menu closes when you die
Menu image name      Make sure to change it in the servertransfer list
Say hook always hiding messages (returned 1)
Gas Mask name typo (thanks, Carnivohra)
Minor code improvement

v1.2:
UMP-45 Submachine gun; this is a fix actually
FN F2000 can be equipped now (thanks, TopNotch)

v1.1:
Console logging when someone equips an item
Workaround to equip items like the Gas Mask and Flags
Performance improvement: Hooks are disabled when not used (thanks to Anomaly)