For sex-oriented builds, the Guards aggression is of little to no importance, just like the battle stats of inmates are. There are even several edicts that the Warden may enact of her own will which will increase the Guards aggression, their sex endurance, prisoners aggression and sex endurance, as well as Karryn's charm. This basically turns almost all the battles into orgies from round 1, where she will only occasionally be hit by an impatient opponent if standing and not involved in a sex act. Pleasing certain types of prisoners (including the guards) grant passives which decrease their chances of attack. In result, you can walk into a Guard battle with 6 of them, and 4 of them will already be aroused and horny. They will be much more aggressive when they invade her office after she masturbated... in a provocative manner to boot, leaving the office door unlocked.I am wary of raising guard aggression since, from what I understand, there is no [legitimate] way to bring it down afterwards (assuming losing their battle results in "it is not increased" rather than "it is decreased", i.e. merely cancelling out the increase from starting the battle).
But it may pose a few problems for such a strict Karryn that you're looking after, if I understand correctly (zero orgasms, zero defeats and penetration limited to BJ only).