If anything, I'd like to see Doran's items become slightly LESS effective to stack...
They give you a HUGE early game advantage, sure, you're sacrficing late game, but i'd like to see the balance shifted ever-so-slightly in favour of spending for late game, rather than securing an early-game advantage at the risk of late-game...
To do this, I'd like to see a portion of the HP from Doran's Ring become Unique...
EG: going from:
+80 Health +15 Ability Power +5 Mana Regen per 5 seconds
+60 Health +15 Ability Power +5 Mana Regen per 5 seconds, UNIQUE PASSIVE: +20 Health
So instead of buying 2 Doran's Rings and getting 160 HP, you would buy 2 Doran's Rings and get 140 HP (60 per ring, 20 unique passive)
Just my 2 cents