I understand what you mean: the nominative object is somehow tied to the predicate and a part of it, as the accusative makes the object a unit of its own right even though it is of course a modifier of the verb.

     What these new examples bring to my mind is cohesion of the sentence. The word order is quite strict in Turkish at least what comes to subject and predicate. Where the speaker is given more or less free hands is in the middle of the sentence where there all the modifiers are packed. Sometimes it is quite crowded in the middle (I know). When the language has the means to mark the object apart from all the other stuff isn´t it logical that this means, the accusative case, is used, especially if the object is physically apart from its main word, the predicate? It simply makes the sentence clearer.

     Besides, what you said earlier about the accusative object whose more details are given later it might be part of the explanation on a semantic level. This should be tested with sentences which have no other differences except the case of the object.

     Maybe the problem can be studied from different corners. You should write and publish an article in order to benefit from it. You are a linguist of course, aren´t you?

Ah no. But I like to discuss subjects/matters about Turkish gammar. Thanks for pointing it out. I hadn´t noticed it because we construct such sentences without any thinking.

     Wow. I just noticed bir and accusative ending in the same word...

     P.S. A couple of sentences jumped into my eyes and they resemble your examples:

     Ankara´ya gitmek istiyorum.

     Ankara´ya gitmeyi çok istiyorum.

     Maybe the phenomen goes to infinitives as well?

Yes it´s similar. I thought the same thing but I didn´t mention it because there was no "bir" involved.