inversion - Where is the subject in "[...] weaker than would otherwise have been the case"?

Where is the subject in the following dependent clause?

[...] Germany adopted a much weaker currency than would otherwise have been the case [...] (taken from BBC News)

Is "the case" the subject? I don't think so. Imagine I re-write the sentence as:

Germany adopted a much weaker currency than would otherwise have been possible

My inability to tell what is the subject in those sentences makes me feel there is something wrong?

If I try to find the subject by asking: "what would it otherwise have been the case?", I would answer the subject is "that Germany adopted a much stronger currency".

The meaning is clear but the grammar feels wrong.

Could anyone explain the grammar involved in this sentence?

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ADDITIONAL QUESTION

This n-gram shows that "than it would otherwise have been" is never used.

Is it wrong to write the following? If so, why?

Germany adopted a much weaker currency than it would otherwise have been the case

Answer

In ‘A Student’s Introduction to English Grammar’, Huddleston and Pullum write that there are three major subclasses of dependent clause. One of these subclasses is the comparative clause. Here’s their example:

More people came than had been invited.

They further note that this clause “has no overt subject at all.” Your sentence seems to be a similar case. We might think the clause is based on “people had been invited”, as for your sentence “it would otherwise have been the case.” But “people” and “it” cannot appear.

Again according to Huddleston and Pullum, one of the distinguishing features of this type of clause is that “they are obligatorily reduced in certain ways relative to the structure of main clauses.” (p. 201) It seems that subjects, predicative complements or degree modifiers just have to be left out, and the sentence in question is one case of this.

Edit: If we take the underlying form as “the case would otherwise have been [that Germany adopted a stronger currency]”, then this would be SV inversion in the comparative clause as @Nico suggests. However, “it was the case that X” seems more natural to me than “the case was that X”. Therefore I would still prefer to treat this as omission of the dummy subject “it” rather than inversion.