MIB's are holding M4s in gameplay now.
I would change cutscene weapon. But Changing Gameplay weapons is correct for me.

Features:
MIB's behind the case in the bobcat were given m4. Idle Armed animation has been added to them.
When the mission started, they were re-spawned, so the m4 was given again and the micro uzi were removed.
It doesn't affect your savegames (main.scm)

Recommend mods:
Beta Leftovers Fix (Csm16)
https://www.gtainside.com/en/sanandreas/mods/142296-beta-leftovers-fix-sa-1-3/

Fixed Cutscene Vehicles (Csbobcat92)
https://www.gtainside.com/en/sanandreas/mods/151915-fixed-cutscene-vehicles/