It's not clear to me what the exact problem is. It sounds like you want to have groupings of weapons, and then use feats to apply proficiency to all weapons within that group. That's actually not the way Exotic Weapon Prof usually works. Typically, taking this feat allows the use of one specific weapon. That said, if you want a feat to apply to group of weapons, you'll probably have to use a foreach loop that searches for weapons with a certain tag (in this case, you might consider making a user tag specific to your group of weapons) and applying proficiency for that weapon. For example, down near the bottom, just above "Sources" is a "User Tags" edit button. Click on that, select "New Tag" and enter something like "Pistol". This will add a tag called "User.Pistol" to the weapon which can be seen in the tags section in the upper right of the editor. Assign this tag to each gun that is a pistol. Then your foreach loop can look for any weapon with that tag and assign proficiency for it.
The loop might look something like this:
Code:
foreach pick in hero where "component.BaseWep & User.Pistol"
perform eachpick.assign[Broadcast.WepProf]
nexteach
Of course, the downside to this is that the proficiency isn't applied until the weapon is already chosen. This is just off the top of my head, though, so maybe someone else has a better way to handle it.