Exotic Weapon Proficiency doesn't grant a +1 to your Base Attack Bonus; that's the prerequisite necessary to take the feat in the first place, not a bonus it grants.
Taking Exotic Weapon Proficiency merely lets you use one exotic weapon without penalty. By the Rules As Written, you can't take it for a non-exotic weapon.
Unless your DM wants to go through and make exotic uses for non exotic weapons. I would say simple things like using a short sword for slashing also, not just piercing. Maybe using some of the reach weapons against adjacent opponents. Might be better covered by a different feat/feats though. Couldn't do anything major though, otherwise the exotic weapons wouldn't be used.
Edit:
Just realized that this is in Rules, not houserules. My idea fits in better there.