Both interpretations are possible but I agree the book's is probably more likely by default. In a natural situation there would be no problem because the context would make things clear.
In theory, yes, though those are the least likely of the interpretations suggested on this thread.
Not necessarily.
I mean that because they agree, the other reading wouldn’t occur to me (personally) unless someone pointed it out, or maybe if the sentence were in a context that made that reading more likely.
When you say that the book’s is more likely by default; do you mean that the accusative is the “default” case when there is a question? I was assuming that the nominative was the default because they occurred first in the sentence?
I don't want to speak for Pacifica, but in my case, what I meant is that the reading with Decem civēs as accusative seems more likely and natural. Your reading is grammatically possible but wouldn't be my first instinct.
Assume that there were no Decem, but that the sentence started with cives. Now, does cives “seem more likely and natural” to be accusative rather than nominative because it occurs before the verb, or because it occurs first in the sentence, or both? How would the sentence be written if cives were nominative?
It could be written exactly the same. As was said before, the sentence is ambiguous; only context can clarify. Now, it's possible to disambiguate the sentence by adding words, like cinefactus proposed, or by chosing a different construction, but that wasn't done here.
How would these be rendered? Would it be the word order?