What? Do you have a source for your conclusion here? I'm not buying moveset being the reason Sakurai didn't choose Bomberman. You basically just said he can make a moveset for Bomberman if he wanted to by saying it would be like Ridley, Megaman, and Pac-man. So since it can happen anyway, there's more reason Bomberman didn't make it. Most likely because they only had enough resources for Castlevania and that was on his mind first. Both series are viable picks because both were possible, both are unique, both are popular choices in the fanbase, and both had potential. It's not as simplistic as moveset.
That wasn't the point of mentioning Ridley. The point was it's very difficult and he keeps it in mind. Moveset issues being part of why Bomberman got an AT role are very possible. Never mind not having any ideas on how to balance him, combined with having two characters he had moveset ideas for. You're literally ignoring everything I said. Resources aren't what made the Belmonts chosen over Bomberman. He made a choice based upon other factors. For one thing, Castlevania absolutely had tons of votes. The idea that he couldn't figure out how to balance a moveset that isn't easy to think about with a high time limit(which made the Belmonts also higher priority) didn't help. It's not a literal case of resources. Those alone doesn't make the moveset workable. If it never danced in his head, it wouldn't matter. One thing he has shown to care about is some form of faithfulness. When possible. But even Ganondorf, for example, is a physical warrior at times too.
I'm not saying Bomberman would be a simple character to implement, but moveset being why he wasn't in was never confirmed by any source. Him being an assist trophy practically confirms he was a consideration. If Sakurai wanted Bomberman in, he would put Bomberman in. Let's not make up reasons as to why Bomberman couldn't make it.
And nobody was saying it was a confirmed thing. What people are theorizing is moveset balance was part of why he wasn't chosen. Where on earth did you get any other idea along the way that it wasn't a theory? It was worded like that the whole time. Bomberman has nothing but projectiles by design(at least only using his own specific abilities). That's why I outright asked for the person claiming he was supposedly easy to make a moveset for to actually provide better examples of how the character could work. Cause a projectile-only character wouldn't be good for balance. They'd be nothing but having too much reach. How would it balance out?
You're combining different points. I theorize that the moveset was too difficult to figure out in a meaningful manner due to the lack of time alone. It was definitely not easy. So he was lower priority. But also lower priority due to the Belmonts being easier to figure out. My reasoning for why the moveset wouldn't be necessarily balanced is a very different point, but may also be part of the same factor that got Bomberman an AT role. Obviously he was considered, for the exact reason you said. I just have a hunch that his moveset was very difficult to balance, so he couldn't see the character "dance in his head", similar to Pac-Man. The problem is that he had to have Namco-Bandai outright help him create Pac-Man's moveset. Pac-Man however was easily viable and did physical stuff beside projectiles within his own series, so it's a lot easier to make suggestions while keeping it balanced. Bomberman doesn't have the same type of moveset design on his own, so I doubt he could've been implemented nearly as easily. Even if Pac-Man used more of his own world abilities, he still has enough that doesn't outright focus on a balancing issue; "All projectiles". Even projectile heavy characters like MegaMan have many physical blows to balance it out.
Though that said, AT's aren't necessarily characters he considers "much". As in, we have no real evidence that he put a lot of thought into implementing Bomberman. He could've been considered, but swiftly dismissed as better for AT. We don't know. It could be Castlevania also outdwarfed him in votes. It could be bias. It just looks like moveset issues are a reasonable factor to think about.