I toyed around with this, actually. Yes, the spreads are huge, but when you consider the spread as a % of the price, and as a function of the pair's volatility, they are much more reasonable than the base figure suggests.
The USDJPY, for example, has something like an 80 pip daily range with a 3 pip spread. That makes the spread 3.75% of the daily range.The USDMXN, on the other hand, has daily range of about 1,070 pips with a 37 pip spread. That makes the spread 3.45% of the daily range.*
*All numbers pulled off of Google search results rather than personal knowledge.
So as long as you manage your position size to reflect the much larger stop and profit targets you will need to set, there is no reason that you can't make money from these currency pairs.
That is not to say that there will not be unique challenges arising from the lower volumes and smaller economies involved. But I would not be at all surprised if there were advantages to be found as well.