Well most character's don't have shields scaling off their primary (in Riven's case: ONLY) desired stat. AP mages obviously do (Lux is probably the only notable one though), supports do but aren't focussing on AP, and most other tanky deeps have them scaling off of AP, which means only Baron Buff + Sheen is their only seen increase of those. J4, Malphite, Vi don't offensively scale I believe.
Malphite and maybe Vi's don't scale with CDR either.
Oh, if I could gut Riven in the right way I would -
Longer CD between individual Qs, hitting an enemy reduces that time monstrously.
Shield decays over time / something about scaling based on enemies present. Maybe Riven dealing damage reduces your shield.
A slightly longer cast time on ult, maybe. If it became a channel instead of a cast, for the rest of time I'll be able to laugh maniacally as you cockblock Riven from bending you over with well timed counterplay.