I think plurals are a fact of life in puzzles and, unless there's dozens (figuratively speaking!), I wouldn't be too worried about it.
I'm of the mind that "the fewer black squares, the merrier," but I, too, would be curious to know what people thought about adding cheater squares in general. For example, I'm currently at 36 black squares (my limit, generally), but two cheater squares would really help me out. Plus, because my theme involves 4 13-letter answers, I already have 6 cheater squares elsewhere in the puzzle. How hesitant should I be about adding more cheater squares?