Would you give a +1 bonus to Fists attacks to a mortal with Might 5 and Fists 4?
Subject to the same limits I mentioned before? Certainly. Although in that case, a more appropriate stunt might be one that just shifts the attack trapping from fists to might.
PS: Compels are not bad things, so using them as a balancing factor seems like a bad idea to me. Sorry, wyvern, I had to say it.
Compels are not bad things for the game. They're not necessarily even bad things for the player; I know I've had fun coming up with self-compels for various PCs I've had. They are, pretty much by definition, bad things for the character, however - and thus not completely unusable as a balancing factor.
Consider: When presented with a compel, you have a choice: either accept and gain a fate point, or buy it off and lose a fate point.
Now, in the buy-it-off case, it's obvious that the PC is not coming out ahead; the player has lost a resource that could have been used to the PCs benefit later, and the character gains nothing that wouldn't have been the case without the compel.
However, the PC *also* comes out behind when accepting the compel. Why? Well, let's consider what a fate point can do: For the context of a single roll, a fate point used to benefit you grants plus two. A compel, by contrast, triggers an automatic failure at a minimum, and often triggers failure plus something else bad - like a broken weapon, or a missed fire blast setting the building on fire, or any spell hexing delicate equipment that you needed to take intact... So even an accepted compel is still overall detrimental to the PC; a +2 is worth less than an automatic failure that doesn't even allow a roll. And that's before you consider that a compel can easily go all the way up to triggering what might normally be a concession or even a take-out result.
Now, where the PC comes out ahead is when they've picked out the right aspects and are getting a compel to do something they would've done anyway - like a heroic type getting a fate point to go running towards the sound of screaming in a back alley. But that's not the case in this suggestion; a broken weapon isn't something that would've just happened without fate points getting involved.