An obvious problem with forcing it to go back to 8v8v8 is that individual skill level is multiplied exponentially in importance.
Let's say that you have 3 people in your team in current FL who don't understand how to survive a dive/burst, that would mean 3/24 die and you still have 21/24 people to launch a counterattack. Now imagine you get those same 3 people in 8v8v8, that's the equivalent of 9 people dying, so now those 3 players are having a far larger negative impact on the team by simply being of lower skill/experience.
This could end up discouraging players that are new to the mode even more, because they cover a larger part of the team and so they contribute more (negatively or positively).