If you're behind enemy lines, chances are the only way to get supplies is by air drop. Instead of placing weapon crates all over the map, have supply drops.
Have Karen Bowman give you the locations of supply drops for turning in intel you've found to her, rather than just getting intel on weapon crates. (I.E. gather intel, take to Karen, she tells you where to find a crate the govt is dropping for your team). The crate depends on the severity of the intel. If you've gathered intel that UNIDAD will be setting up an outpost on top of a mountain, for example, then your drop might be a new more powerful sniper rifle. If you get intel that a large size force will be coming for your team, perhaps an LMG will be what she asks for and tells you where to find. It should be an item (or items) that will prepare you for whatever intelligence you've discovered.
Place enemies at or near the crates. A giant parachute wouldn't go unnoticed by locals. Make the ghosts fight through some cartel/UNIDAD to get their gear before the cartel does (even if the cartel don't really ever take it, just put some around it, or script them loading it into a truck when you get there and give the team 45 seconds to stop them, if they don't, the truck leaves with the crate and the ghosts have to chase the truck down, or something like that).
I dunno, just an idea I had. I don't like the current way we just randomly FIND weapons. Having supply drops makes more sense. It also gives gathering intel a purpose instead of just drops, it provides Bowman with real sensitive site exploitation intelligence that can be used against the cartel and help further your fight, and double as a reward in a sense. It also adds another "side mission" element to the game.
EDIT: Perhaps the intel locations could be specific to the weapon/attachment it unlocks? I.E. There's a Lieutenant in Itacua at one of the farms that if you interrogate him, give the info to Bowman, you unlock the location for the ACR, etc. etc. However, you wouldn't know that going in, but it is information that the community could share with each other as they progress. I.E. "Hey guys, go to XYZ and find the intel on the desk and take it to Bowman to get X weapon!" -Thanks to /u/Gwyndon for his post. It helped me think through this.