Context: Bob is angry that event X happened today. A series of unfortunate events throughout his life led up to this crappy day, and thus he thinks to himself, "if only things were different". How do I translate this line when 'things' refer to 'basically everything bad that has ever happened' and is so vague and all-encompassing that even Bob doesn't know what specific things he's referring to?
I'll translate freely the entire given question into natural Japanese by replacing Bob with 恭一{きょういち}.
あらすじ:恭一{きょういち}は「あれ」が今日{きょう}起{お}きたことに憤慨{ふんがい}している。彼{かれ}の人生{じんせい}のいたるところで顔{かお}を出{だ}す「あれ」が、今日{きょう}という日{ひ}を台無{だいな}しにした。恭一{きょういち}は誰{だれ}にも言{い}えない憤懣{ふんまん}を吐{は}き出{だ}すように言{い}った。「あれさえなければ…」。 確{たし}かなことは「あれ」とは恭一{きょういち}にとって「これまでに起{お}きたあらゆる悪{わる}いことの全部{ぜんぶ}」を指{さ}しているということ。しかし、実際{じっさい}には、何{なに}を指{さ}して「あれ」と言{い}っているのか恭一{きょういち}自身{じしん}定{さだ}かでないほどそれは曖昧{あいまい}だがしかし一括{ひとくくり}りに出来{でき}そうでもある とき、"if only things were different"を日本語{にほんご}ではどういう風{ふう}に言{い}えるのだろうか。
The answer to "if only things were different" in the context is "あれさえなければ" and "things" in the phrase is "あれ".
I think "あれさえ違っていたら" couldn't express the nuance of "if only things were different" in this context.
EDIT
I know あれ means a pronoun indicating something distant from both speaker and listener (in space, time or psychologically), or something understood without naming it directly, but I used あれ for "things" in the given context.
I also know the "things" is said that even Bob doesn't know what specific things he's referring to.
But the "things" is defined clearly as "basically everything bad that has ever happened" in the context. The definition means that not only today the "things" happened but also the "things" happend everytime when bad things happened to Bob.
From this fact, I understood that the "things" was clear to Bob or at least he could make what happened to him clear whether it belonged to the "things" or not, but he couldn't address it with a proper word just like the questioner couldn't because there was not any exact word to express this complicated concept.
The very good interpretations with 「状況が違ってさえいればなあ。」, 「こんなことに(さえ)ならなければなあ。」 or 「こんなこと(さえ)にならなかったらなあ。」for "If only things were different" by Chocolate couldn't cover "basically everything bad that has ever happened", so I darely invented あれ for the "things".
If you read my free translation in Japanese, I think you could understand the use of あれ is a somewhat good choice though it is not exactly correct because there is no exact word also in Japanese.