The idea of Kira being a DLC only character might cause ire to some fans, or even just an oddity of why he isn't included. That is until you realize that Kira technically is in the game in the form of JoJolion's Josuke.
Lessened somewhat with the reveal of Kosaku, who is also Kira, who IS in the base game.
Dio treating his son well makes some sense when you think about it. He hated his dad's guts for being an abusive drunk, so he might strive to be a good father to his offspring in order to be less like him. Granted, this is Dio, so he'd probably show his concern in really...unusual ways.
Funny Valentine's Love Train can't block projectile GHAs. While we see both Gyro's Ball Breaker and Johnny's Super Spin breaking through the barrier in part 7, Kira has no such excuse. Until you realize that Sheer Heart Attack counts as part of Killer Queen, not as a projectile, while Bite The Dust enters the opponent's retina when he/she sees it, and thus it bypasses the barrier completely. Hol Horse also uses the retina stunt via the Hanged Man, distracting Valentine long enough for a opening with the Emperor. The most glaring example is Mista's, where the only thing that allows Sex Pistols's bullets to break through Love Train is via raw sheer force
Iggy being later DLC and not part of the base game's initial roster references how he didn't actually join the good guys until well into Part 3.
Santana, ACDC, The Cars, and Wham! (well, and REO Speedwagon) were all bands formed during Joseph's lifetime, AFTER he fought the Pillar Men.