Not to be that "SynthV master race" guy but, it would have been interesting to see what cross-lingual synthesis on Vocaloid would have been like (and I say it like that because I doubt they are gonna do it when 1, Vocaloids come in 5 languages and 2, Vocaloid AI is not public*), and my thoughts and ramblings on the idea:
1. Their English would be similar to existing Engloids but with accents. Gumi would sound similar to her English voicebank but the Cryptonloids would sound very different.
2. oh shit they have appends too would they get language updates too?
3. Oh wow, finally more Korean and Spanish Vocaloids since they never made more than 2-3 :D
4. More westerners would use the Vsingers
5. We would get voices in languages that don't have any alternatives (e.g. Sachiko! also Wil, I wish there was an English alternative to him so bad (but it seems like the only soft male English Vocaloid is Kaito. Though all 3 members of Zola Project have been compared to Hio who really just sounds more like Kyo or a higher-pitched Dex to me))
Edit: * 3, there's a lot of Vocaloids to begin with so it would be too much to program now and 4, assuming it would be V5, V5 is huge to begin with.