There are a wide range of accounting methods for companies to choose from. The fact that there are so many methods could make it difficult to compare and interpret financial statements. The conventions of full disclosure and consistency mean companies must be clear about how they compiled their financial statements and this alleviates some of the problems in interpreting the varied statements.

You're right about latitude and could cause. The are the subject and verb. The section of the sentence that starts with "were" is an independent clause. Notice that the part before it is a complete sentence on its own. I would have put a comma before "were" to make this clear. Since it's a clause not a sentence, it doesn't need a subject."were it not" is a common inversion used with these words. To clear up the inversion, replace "were it not" by "if it were not" or even just "if" and avoid the "were" altogether. Note: you need "were" not "was" here because it's a hypothetical so you are in the subjunctive mood.

the "were it not..." could be substituted by "if it was not ..."