All the obvious choices I would want have already been said (Piko, Sonika, Lily, SeeU) so I guess I'll say maybe MAYU? I feels like she really has the potential to shine if EXIT TUNE gave her more attention. She had some good songs when she first came out.
I’d love for Mayu to get an update, too. She’s got a gorgeous voice, but has the slight talk-sing thing going on. If they updated her, fixed that, and made it really good, I’d low key be willing to buy V5 just for her. (Come on, Exit Tunes! Give your girl some love!!)
Maybe if she got an update and it was really good, people would give her some more use.
I'd have to say Leon. He's one of my absolute favorites, I love his voice type, and out of all my favorite Vocaloids he's the one that would benefit most from an update. He's nearly impossible to get these days, if you do get him V1 can be a pain to get to work on modern computers, and overall the technology behind his voice and V1 itself are completely outdated. He and Lola were my first picks because they're simply just the most outdated, but I just like Leon more so he wins haha.
Lily got pushed to the side after her V3. Vocaloid's like Gakupo not getting updates can be explained because the VP became so expensive to hire Internet Co. couldn't afford to update him.
Yuri Masuda has recently come out of retirement and I believe she expressed interest in doing more voice work for Lily. Lily as a Vocaloid always felt underappreciated to me and I genuinely think she deserves either a V4 release or a release via CeVIO. I'd love to see Appended voicebanks like Soft, Power, Dark, or possibly English, since Yuri Masuda has sung in English in the past.
I would love to see what the redesigns for the appended VB's would look like. Maybe they'd be based on different types of Lillies?
Also, I love Lily and I will die for her, so there's that.
out of my most used favorite loids, most of them have had pretty solid updates last time they were updated.... and if i had to pick just one bank id definitely say one of the V1s... probably Leon because i prefer the masculine banks. itd probably be the coolest to see Leon updated considering the V1s are unlikely to ever get a real update (as in, using their previous voice providers to rerecord). and the improvement to see between the old in new would just be crazy cool in my opinion. i would love to see such a direct comparison of old and new.
if i had to pick a second due to others mentioning leon... how about Galaco, though i feel something based on her Blue bank would be best? i feel like she has a lot of potential mostly her blue bank and man, she does not get a lot of love.
Figured I'd update my opinion... kinda I still agree with my stance on a Sweet Ann update cause I can't shut up about her sorry... kinda but also not really cause have you heard Sweet Ann :< her voice is perfection voiced by an angel
Buuuuuuut I would also say I feel CUL would really shine with an update like I kinda feel that metallic twang is part of her appeal at this point? but at the same time I wonder how would she sound without the recording complications :< I think she would be an extremely versatile voicebank if she was updated i suppose XD