You could also get the community involved in providing the subtitles. I mean, official subtitles for the theatrical versions exist, right? So you just need them for the new scenes. Or… How much work would it be to commision real language speakers to contribute?

And as far as that Trelawny scene goes, I remember some old fan edit using both the theatrical and the deleted scene, by just going back and forth between them, having a bit of each.
I don’t think split-screen would be fitting, it could just get very distracting.