You can still just play 1 civ then. It's not a big disadvantage in a game with so many people. Make 1 good ally. Bam you've evened things out no problem.
And I think at least 15-20% of people would like to make a second account. Maybe more. The negative effects seem extremely small and the positives considerable. At least in terms of longturn. Smaller games it could be a bigger issue but who cares about small games? Longturn is where it's at.
No, it's not just to make an ally to even it out. An ally doesn't transfer all his cities and gold to you.
I can't believe anyone actually endorses multi-accounting on this forum. Considerable positive sides and extremely small negative effect? What will happen if multi-accounting gets to be common, or perceived as common is that the people that actually want to play a good fair game leaves, and this will leave game in ruins.
If there are that many people that multi accounter freeciv, go ahead make a fork. I bet it will be fun.