The mentality that there are "competing" roster slots exists because, in truth, there are only so few spots left, and not everyone is going to get what they want.
However, given that Banjo is a 3rd-party from a 3D platformer on the N64 and Isaac is a 1st-party from a turn-based RPG on the GBA, I can say with certainty that they have nothing to do with each other's chances. Frankly, they both have a fantastic shot of getting in. So instead of ****-measuring sales figures from two decades ago, let's agree that while we all have our wants and desires for characters, we shouldn't let said desires cloud our judgment on other characters. It's a tense few months for fans of any character, no need to make it worse.
Moving on back to Banjo, to the realistic animal noise point, I can actually see that happening unfortunately. I would be disappointed, but have grown used to DK, Diddy, and Bowser already so I'd learn to live with it.