if only usage: leave out the 'was'

When ‘it’ refers to a letter or a complex situation projected to be caused by a letter, is it okay to use ‘if only’ in the following way? Why or why not?

"It’d all be appropriate if only written by any other person."

I understand that I can always say "if only it was written by any other person", but that seems wordy.

I guess here, the ‘it’ could either refer to the letter or the situation caused by the letter, and I’m okay with either. But strictly speaking, perhaps only when you interpret the ‘it’ to mean the letter itself can you leave out the ‘was’?