I really don't want six variations to all involve using Metal Blades. That we're promoting such centralization around the move means Shadow Blades/Hyper Bomb aren't going to get the attention they deserve. Heck, Shadow Blades already is least explored of the three Neutrals. Yeah it's straightforward and has less range and damage than MB. I just like having the option of not potentially handing my opponent my item, instead having a projectile that can still hold them down but is more spammable .
Instead it's "how can we fit all our other moves around Metal Blades". Oh, rather not use MB? Too bad, out of luck, BYO3DS.
At this point I'm kind of hoping we can be allowed slots 7 and 8. Right now they're apparently reserved for people to take customs for a test run, but I feel people can do that on their own system on their own time, or at the least not every system needs to be given that set.
On the one hand, I hear you, there may be some potential to Hyper Bomb and Shadow Blade that we're just not seeing. Hyper Bomb has some interesting qualities when it comes to z-dropping and glide tossing, and Shadow Blade has some combo potential with MM's otherwise very unsafe kill moves.
On the other hand, I've tried all 3 Neutral B variations in friendlies and Metal Blade just seems to be the best, no contest. It just has a lot of useful qualities that the others don't have: speed, power, range, ability to easily convert to item form, proven combo potential (including the now infamous MB -> utilt combo).
Hyper Bomb is just too slow and cumbersome. It's hard to use against anyone putting on an even a little pressure, telegraphed and easily avoided at a distance, and difficult to get into your hands as an item.
Shadow Blade is weak and lacks range. Yeah, you can sometimes use it to trap opponents into a utilt or usmash, but you can do the same thing with diagonally thrown MB and item MB, respectively. You give up the power and versatility of item MB (including all the fun z-dropping and glide tossing approaches and end guards). In exchange, you get a short range projectile that can't get caught but will still get beaten by many dash attacks and aerials. Just not worth taking IMO.
If there's one move I think this board is sleeping on, I think it's Tornado Hold. Lot of edgeguard and stage control potential there.