Hi Ali
'it would have been ideal' is what we call a third conditional in English: it's used to talk about an action or event that didn't happen in the past. As we're talking about something in the past, there's no possibility of happening anymore!
Some other examples that could make the explanation easier:
If she had asked me out, I would have said yes.
If you had asked me, I would have helped you.
If I had trained harder, I would have been a footballer.
Kind regards
Karen