I think it would just mean tanks would powerspike earlier, and then fall off just as hard as they do now, while bruisers would powerspike later.
Like a lot of other people keep saying, the best way to make tanks stronger is to give them abilities that scale off of their own defensive stats, for Example, Braum has several defensive scalings, Garen and Mundo have health linked scaling, Rammus has Armor scaling as does Malphite, Galio has MR scaling (and is actually REALLY strong if used as a counter pick). The only other thing that can help out a tank even more is giving them straight up damage reduction, like Maokai or Alistar.
Tank kits ought to incentivize building tanky, and should reward building tanky by multiplying that tankyness. Fighter kits ought to be either continuous low DPS with high durability and utility (bruisers), or continuous higher DPS with lower defense and utility (fighters)