There was never a "big 4" or "unbreakable team" of Smash requests. Not everyone who wanted Ridley also wanted K. Rool, not everyone who wanted K. Rool also wanted Banjo, not everyone who wanted Banjo also wants Geno. Outside of some surface level similarities between K. Rool & Banjo and K. Rool & Ridley there is absolutely nothing tying these characters together beyond "they were on Nintendo consoles in the 90s and don't appear much nowadays" and no reason one can't join without the others.