System Admin Read-only analogue to System Administrator would be one of the most desired features that we are missing.

System Admin Read-only role will cover 90% custom access requests for Environment Access in our organisation.

Lack of Admin Read-only role often results in granting System Administrator role and asking not to modify any data…

this is wrong, however urgency and lack of out-of-the-box or custom-build read-only roles often force organisation to accept the risk, especially in non-PROD environments.