Can が be replaced by something else in this structure?

Question

So reviewing basic grammar I've come across a structure where you use は and が to show contrast in the following way:

(私は)土曜日は暇ですが、日曜日は忙しいです。

This sentence sounds right to me, but it would sound right like this as well:

(私は)土曜日は暇ですけど、日曜日は忙しいです。

And I'm a little confused because all the books and websites I see explaining the 〜は 〜が 〜は structure make it look like an exact sentence pattern that you can't change, and I'm not sure if that's because it's incorrect otherwise or because they don't want to make it too complicated for beginners.

So is this a closed structure that can only be done like that or can you insert any other linker to show contrast in the middle?

Apart from that, something else that confuses me a little bit is the double は in the sentence. I'm not talking about the two はs after each contrasted element, but about the は after 私. I've never quite understood if a sentence can have two topics or not, or under what circumstances. So if you're familiar with the topic, even if you can't explain why, could you please confirm if that's correct?

Answer 1

Conjunction が has nothing to do with particle が and the は・が problem. Only difference between 暇ですが and 暇ですけど is that the latter is more colloquial. Apart from that, they are the same.

I'm not talking about the two はs after each contrasted element, but about the は after 私. I've never quite understood if a sentence can have two topics or not, or under what circumstances.

"Topic" or "contrast" are not substantial concept. They are only two different explanations about an identical thing. (So, there's no grammar to restrict use of multiple は whether it's topic or contrast.) You use は for several reasons, and some grammarian thought of what those reasons have in common as "topic", and the other grammarian thought of it as "contrast". In the field of education, both "topic" and "contrast" are used to make things easier to explain. What's topic and what's contrast depend on your interpretation. In reality, "topic" and "contrast" are not enough to explain various use of は. That's why this problem continues to confuse learners.

• 日本では果物が高い：Fruits are expensive in Japan.
• 日本で果物が高い：Fruit price is rising in Japan.

Wrapping up this kind of difference with "topic" or "contrast" is not really useful for learners, is it?