Had my father live one year longer, he could have attended my wedding ceremony, but just because I was indecisive for so long, I couldn't give him the chance to see me in my wedding dress. I feel so sorry!
ex#5491 知ってるのであれば、教えてくれてもよかったものを。"If you had known, it would be OK even you told me."(But now it means not OK to the speaker since before this , the listener DIDN'T KNOW about that particular thing and told the speaker about it already.) Sounds strange to me, unless the speaker wanted it to be known to him at that particular time , in that case : あの時知れば、教えてくれてもよかったものを。 Is better to say : 知ってるのであれば、教えてくれてよかったものを。or (君が）知っていて教えてくれればよかったものを。"It would be nice if you had known and told me." I think if you wanted to say : " If you have known, why didn't you tell me?" (Of agony) : 知ってるのであれば、どうして教えてくれなかったのよ．． "If you have known, isn't it ok to tell me?" : 知ってるのであれば、教えてくれてもいいんじゃない（か）。
You have to keep in mind that ものを is not a conversational phrase, and it is predominantly literal diction.
I don't thinsk it always used with 〜た形。blabby's exmples are all natural to me.
Miki and blabby are right. It doesn't have to be 〜た形.