(Deep down inside, I do agree with that system of 200 rolls for 1 SSR but that would be too nice)
If something could happen to USO, I think they could change it to:
-You can get 1 USO per banner as long as you roll 500 SQs or more and it is limited to only one per banner. (There would be a count to see how much SQs you spent on the banner similar to how they count Free Quartz and Paid Quartz)
-Story summon USO would be reset every months (This is to bait players) so you can get 1 USO if you roll 500 SQs on Story a month.
-All servants’ USO cost lowered down to 5.
I feels that it does give a more incentive to rolling hard for one banner even after you already got the servant and it would still benefit players alike even if they get shafted.