NGL It kinda feels like people are severely underestimating the possibility of CP7 being first party, especially if they were indeed going to be revealed at E3 alongside Min-Min.
Why do I think that? Because If CP7 was revealed after Min-Min and is a big third party like, for example, Crash, it’s very likely that the former would be completely overshadowed by the latter.
Back in E3 2019, as we all know, both Hero and Banjo-Kazooie where revealed. They where both big third parties that were popular in two different parts of the world ( Hero in Japan, Banjo in the west ) but weren’t unpopular in the other's country either. As a result, neither one overshadowed the other.
Now, let’s compare Min-Min to the likes of Crash. Min-Min is a small first party character from a three year old game that gained surprisingly moderate success for a new IP.
Crash, on the other hand, is a big third party character from an over 20 year old series of games with one of his latest being a highly successful remake collection of the original trilogy and has a long awaited fourth entry coming out soon.
So, if Nintendo’s plan really was to promote ARMS as a series they want to give attention to by adding one of the game’s characters, I don’t think it would be a smart business move to reveal a WAY bigger character right afterwards and taking the spotlight away from ARMS.
That is the reason why I believe CP7 could very much be another first party character, one that would either be of equal popularity so that neither them nor Min-Min would overshadow each other ( just like Hero and Banjo ), or, at the very least, one that may be a little more popular then Min-Min but not enough to hog all the spotlight from her.
But the question is, what first party characters would fit either one of those criterias?