It is very easy with to work with the publisher, but it is often difficult to work with the developer (sub-company).
For example, this was my response for why Master Chief couldn't appear in Smash:
This is the followup response when someone fully understood the original intent behind the message:
After I post these responses, I went to do more research on what else 343i did with the
Halo franchise and if they causes any controversy recently. And I found this
controversy that was post 3 months ago, and it basically boil to 343i not Microsoft that causes this issues. Remember 343i is the one who currently control the
Halo assets after Bungle left Microsoft and can determine whether or not someone else can property uses the very same asset from
Halo into their own project like
Red vs Blue or into a fighting game like
DoA or
KI.
The only time Master Chief the character have officially appears in a actual crossover for a video game was
Super Bomberman R as a Microsoft exclusive character. Even then, that MC is a alternate take/counterpart, and therefore this alternate character doesn't conflict with the supposedly 343i/Bungle's reason for why MC can't appears in other games as the current
Halo timeline/canon isn't conflicted. This is also another reason for why MC can appears as a character skin in
Minecraft as that appearance doesn't involved the
Halo timeline/canon.
Microsoft can be a easy publisher that Nintendo can worked with, but 343i is the one who could pose the bigger problem for why Master Chief can't appear in Smash unless Nintendo is okay with the suggestion of Master Chief being a Mii Costume for a Mii Fighter. Master Chief being a spirit isn't possible since it involve the actual likeness of such character and this conflict with Bungle/343i on the whole
Halo timeline/canon. I wouldn't be surprise if Master Chief didn't appears in the current Fighter Pass 2 or any future Smash game(s) as along as the suppose
Halo timeline/canon is involved.
Once again, I am perfectly okay with anyone joining Smash if it makes in context.