Imagine there's a very short question at this site, and I'm uncertain what the poster intends to ask.
Should I write
- It would've been great if you'd expanded your question. (matrix clause: Past Perfective modal, conditional clause: Past Perfective)
- It would be great if you expanded your question. (matrix clause: Past modal, conditional clause: Past)
- It will be great if you expand your question. (matrix clause: Future modal, conditional clause: Present Simple referring to the future)
I'm not sure about sentence 1. The verb "expanded" calls for a future action, but in sentence 1 we describe an unfullfilled condition in the past.
Or maybe the construction of sentence 2 is used to refer to a situation that is already "over" and it too far in the past to serve as a hint that I want more infornation now. Maybe such construction would be more suitable in "I remember that question you posed 2 years ago. It would've been great.."
Sentence 2 is what is called a "second conditional", and it is said that a second conditional describes an improbable sutuation in the present. Would it be suitable?
Or does the verb expanded makes the first two options awkward semantically?
Sentence 3 describes an open (possible) condition, but isn't it a bit too mandative?