I don't know of very many bands that release really old material on their newer albums.
It happens. Dark Tranquillity put a song written in '96 on a 2010 album. I don't think it would happen here though.
Sorry for being a buzzkill, but the only could-have-been version of FII worth discussing is the demos. This way, if we're discussing ACOS on FII, the only fictional scenario we could consider is having the rest of FII written somewhere in '95 to accompany it, and we have no idea how would those songs sound like.
This way, everyone would take away (my pain) different songs from the actual album and add different songs from the demos, so we can't get a definitive fictitious version to discuss anyway. And it doesn't make much sense, having ACOS there, seeing how much they wrote for FII, I don't think they would have had an older song on the album assuming they hadn't released it already - kind of like the case of IAW and DLPM/TLF. You could have asked the same thing about having those tracks on the album, or Eve, or something.