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

Question

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 1

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.

Answer 2

To Complement @user2619 's answer

I would like to complement @user2619 's answer with another piece of information that I managed to find in the Longman Student Grammar of Spoken and Written English.

In Table 12.3 "Special types of inversion in dependent clauses", I find a case that I think it is relevant to answer my question:

comparative clauses with "as" an "than"

Independent agencies are in better position to offer personal service than are those tied to big chains.

This table explains that in this type of sentences the operator ("are" in the case above) follows the subordinator (in this case "as"). Using this interpretation I can say that:

• the main clause is "Independent agencies are in better position to offer personal service".

• the dependent clause is "than are those tied to big chains".

• the dependent clause shows a subject-verb inversion, and without the inversion the clause would be "than those tied to big chains are".

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And the full answer to my original question

Combining this information with the information in @user2619 's answer, I'm now able to interpret both sentences:

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

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

The first sentence can be interpreted as an example of the subject-verb inversion described in Longman Student Grammar of Spoken and Written English.

And the second sentence can be interpreted as an example of the obligatory ellipsis described in "A Student’s Introduction to English Grammar" by Huddleston and Pullum.

Answer 3

The subject is "it" which is not mentioned before would.

... than it would otherwise have been the case