| | Re: Help with "May God have mercy on your soul"
If I were you is the regular second form of the verb "be"
Rule - form: second form verbs are not marked for person or number - eg I played, he played, they played / I went, he went, they went
Rule - use : second form verbs can be used to express A) past events - I lived in Finland for a year B) hypothetical events - I wish I lived in Japan
The verb BE is unusual in that for use A (past events) it uses an irregular form which is marked for person/number - I was /He was/We were/They were in Japan last year - but for use B (hypothetical events) it uses the regular form with no person/number marking - I wish I /he/they were in Japan
See Palmer Grammar Penguin