FWIW, I'm not sure if the English DTS you're referring to is DTS-MA or not, but often DTS-MA tracks have unnecessarily large lossy DTS cores. If you uploaded the track somewhere, I could extract the lossless PCM using Arcsoft, and then re-encode the DTS-MA with the smallest possible lossy DTS core, which could save some space.

And if it is DTS-MA, I think you could safely drop the AC3 version unless the content is really that dramatically different. Pretty much all Blu-ray setups should at the very least be able to play the DTS core.

EDIT: ...and more people speak Japanese than German or Italian, and possibly more than French depending on your source of info. Just sayin'.