What about Borderland Minotaur?

I kind of like its interaction with exploit, and it should be fine at common. Brackwater Elemental and Fog Elemental were commons. Mardu Blazebringer is the only precedent in red.

On the other hand, we do have 3 red three-drops and only 1 four-drop, and no red vanilla creature.

­Gore Swine Can fill a similar role but be both more appealing and more elegant.

How about making the creature bigger and removing its ability to block? Kind of like a slow Ball Lightning?

Personally, I would turn this into a 4 mana trampler with 1 health instead of a Gore Swine. I don't like the idea of a 3 drop getting swatted by a Thopter.

What about a Lightning Shrieker style creature at 4 drop?

Lightning Stalker
Creature - Elemental
Menace, haste
At the beginning of the end step, ~'s owner shuffles it into his or her library.
4/4

And yes, I know this still doesn't fill our vanilla problem.

After a bit of research, it does appear red is not FORCED to have a vanilla if it furthers our set. But it seems it is most of the time replaced with a french vanilla. (For reference, both sets of the recent Zendikar block have no vanillas in red commons.)

Being able to exploit this is the whole point.

We already have Perilous as a perfect target in red. At the very least, I don't think we need a second target that goes extremely well with Exploit in red commons. I do see how LS isn't exactly Exploitable.