If Riven is left as one of the only brusiers in the game with no innate armour pen/true dmg/% health dmg then she has to be balanced around not being able to play the game at all against tanks while running over squishies in lane with no counterplay. If you allow some sort of tank busting into her power budget, she can be balanced to be more well rounded. There’s not much stopping Riven from going mid lane and destroying mages with her buffs if she cannot deal with any bruiser or tank that builds a little bit of armour.

The only reason Riven is the way she is currently is because Riven is an archaic champion. There is no way a top laner would be released nowadays with no way to fight against champions which build resistances aka most top laners.