Re: star with one tense and end up with another
All of those examples would work better with the present perfect in the second part, because they relate to what is going on right now.
I've been asking.... but she hasn't agreed.
I've been reviewing... but I haven't memorized.
We've been kicking around... but haven't come up with anything.
I hear over and over (ad nauseum) how Americans don't use the present perfect (although I'm not referring to your post in particular, abpl), and we do. Really. We do. I have found that "Did you... yet" or "I just [simple past]" are examples where we use simple past where others use present perfect, but that doesn't mean we just use it wherever and whenever. I would not use simple past in your examples.
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.