It in it seem that vs. it seems like

It seems that John is happy.

It seems like John is happy.

We're all familiar with the fact that it can be used as a "dummy it" that's semantically empty, but I have a feeling that the it in the 1st example is more dummy-like than the one in the 2nd.

Assuming that the that clause in the 1st example expresses the same thing as its subject (namely it) does, I believe what I'm saying is quite reasonable.

In fact, a that clause can be a subject, while a like clause cannot.

That John is happy seems to be true.

*Like John is happy seems to be true.

This may imply that the it in the 1st example refers to the subordinate that clause, but the one in the 2nd example doesn't refer to the subordinate like clause.

But I'm worried if this really makes sense, and so I want to get to know whether it's possible to put an emphatic stress on the it subject in the examples at the top.

I know it'd completely depend on the context of the utterance, but I'd like you to check to see if the following sentences are acceptable.

IT seems that John is happy (not THAT).

IT seems like John is happy (not THAT).

I'm aware that it's best to just say what it refers to (I mean, THIS seems like John is happy would be better than the example above).

But, I'd like you to tell me whether it's possible to put such a contrastive focus on it.

Thank you in advance.