Question on IO utilization capacity

Just to give a background, many times we encounter situations where the flash cache response time increases to ~10ms for the small reads and impact the oltp workload, and it happens mainly when we have a lot of full scan/smart scans happen from the warehousing type workload at same time. And during this the flash disk Io utilization reaches up to ~80% with large reads showing ~30K IOPS. Similarly another exadata box on X3-2 with FULL RAC with multiple databases mounted on it though and ~20TB flash cache(Write through), and we are seeing a spike in hard disk response/IO utilization but not such spike in flash disk response or IO utilization.

Now we are definitely working on making the application queries better but as part of tech refresh, the infra team already has a plan to move to a new exadata box , so management is asking, if having a full rack or additional storage cell servers added, would be helpful in making the above situation better? Or say having more flash cache allocated with the same number of cell servers will help us create some more capacity? Want to understand experts' thoughts on the same.

Regards