That may sound extreme, but since the rules ensure priority has to pass all the way around the table (in turn order, starting with the player whose turn it is) before each spell resolves and between each step and phase of a turn, everyone is still able to play effects at the moments they need to
Load him up with a bunch of weaponry and tools, and he could become a powerhouse albeit one with the Achilles heel of staying at base toughness
Panharmonicon isn't a super widely played card despite the popularity of ETB cards, so I don't expect to see Elesh Norn outside of dedicated ETB decks or in tables that aren't expecting powerful cards like this one
The exiling of the spell with Suspend is what makes this so fun that spell that comes back eventually is gonna trigger Flurry again for you
Haste Plenty of red creatures start with haste, and some of its cards can even grant it to others
But theres technically nothing stopping this from happening in future if WotC decides to print something to interact with them
