My ideas for a rework/retune
Paragon of Demacia is now Poppy's passive: Upon dealing or being dealt damage Poppy gains a Paragon stack for 4 seconds, stacks up to 5 times. Pagagon stacks give armor + ad: [lvl 1] 2 arm + ad per stack, [lvl 6] 3 per stack, [lvl 12] 4 per stack.
Devastating Blow: Poppy puts all her strength in to her next attack, 5 second window. Once Poppy has swung her hammer, either on-hit or (maybe) reactivation, the force of the blow carries Poppy through her target dealing damage in an area around her - She's carried forward as her hammer spins a few times or she sort of flips over her target and slams the ground behind them. The main thing is Poppy moves and deals aoe damage when her Q hits.
W is some new ability. This is an idea I had but it's kind of terrible because I think Poppy would need something better. - Valiant Fighter: Active - Poppy gains max Paragon Stacks and has 2x their value and MS for x seconds. Passive - Poppy gains (spell rank) scaling MS at max Paragon Stacks.
Heroic Charge: Same ability; works really well with the movement from Q.
Diplomatic Immunity: Removes damage immunity and instead makes Poppy more resistant to damage. She's more resistant the lower her health and [maybe] deals more damage to her target the higher her health. Resistance and damage amp have base values so the spell is relivant at all health percentages. - The name is kind of odd with the effect changed
Simple kit that keeps Poppy's feel while addressing some of her lane weaknesses (mobility + wave clear) and absurdely strong components (passive + ult). Well in my eyes at least