Please stop suggesting a switch to MMD models. That's already out of the question and it's just derailing the thread even further. Smash messes with canon as well. As long as the outfits are made with consideration for the character's personality, it's fine. The ONLY design I would mess with is Rumia, assuming she uses her silly "arms outstretched" stance. The reason why we consider that look iconic for Rumia is because it reflects her childish personality. That just doesn't work well with her model's skirt, both because it has a more mature look to it, and because the silhouette would be really different. There are other characters where creative liberties like that can be taken, but big and wide skirt is the way to go for Rumia IMO.
Anyways, I really feel that your presentation for WIPs is hindering you here Saijee. The way Tenshi and Sakuya look in the first post is actually pretty good! I understand that a neutral pose and expression might be the best way to show every detail of the model at once, but it also doesn't convey as well to non-artists what the character will look like in-game. The neutral expression in particular is really off-putting at times... If you look back at
the Smash Brothers examples that game2011 posted, you should note a few things:
1) Even when characters like Zelda and Palutena are in an idle pose, they have an expression that reflects their personality. Zelda has a somber expression most of the time (does she ever even smile in the game?) and Palutena looks halfway between nurturing and condescending, which is perfect for a god who is lowering herself to fight among mortals. This is a CRUCIAL part of differentiating your characters. Truthfully, this isn't something that ZUN excels at in Touhou canon either, but you can see hints of it when you compare say, Kanako to Byakuren.
2) The facial features have variable shapes and angles, not just sizes. Link has extremely angular eyebrows and a rounded nose, conveying that he's a youthful and determined character. ZSS's expression is more relaxed, showing that she's a fighter who's calm under pressure. The shape of the face itself also matters: Peach's design, face included, features a lot of roundness. What do you do think that conveys compared to Zelda, who has slimmer and sharper elements to her design?
I don't think Touhou characters need unique expressions to the same extent, but when you post expressionless previews, you're drawing attention to that lack of personality. When I visualize how a character should look, I see not just their design, but their expression, and that's probably where half of your criticism is coming from! The models don't need a huge fundamental change, but small tweaks to give the more character would help alongside more expressive previews.
Sorry, if this isn't of any help to you, since I don't work with 3D at all, I just have a lot of interest in character design in general. I hope you can see that I'm not just saying "look at Smash Bros, do that" but rather "look at these elements that made Smash Bros. look good, and see where you are lacking them in your own work". Best of luck, and I might post a moveset or two later when I'm feeling inspired!
(I see you posted while I was typing, but yeah the new Sakuya is better, I'd just rather be seeing her in "determined maid" mode, heh)
EDIT:

Here's a nice example by the famous
Captainski of Touhous with lots of facial differentiation while still having a consistent style.