I would be surprised to see any CIA official current or ex, to want to maintain the FISA system at all costs. FISA warrants are almost ALWAYS granted. If the FISA system has been abused, then the FISA warrant system and its status in regards to confidentiality in that particular instance should not necessarily be retained, but not necessarily needing to be aired in a public court of opinion.
Abuse could include, but not be limited to, falsely swearing to facts to obtain the FISA warrant, or attempting to twist the use of the FISA warrant/investigation as an excuse to commit illegal acts, or criminal offenses, as perhaps in the allegations of political weaponization in this instance.
If this is the case, and there is enough evidence to prompt further investigation, then a special prosecutor should be assigned to investigate the claims and the entire scope of wherever the investigation leads are fair game.