On this page I wil try to find out if it is possible to predict the Skill Tree for a Troopers with Frenetic as a starting ability. I think that all possible upgrades for each trooper are defined at the moment he is recruited. It could depend on the combination of the two starting abilities and the name.
If you have a Trooper with Frenetic as starting ability please add him with name and all following abilities in the list as below.
Jackones: Pistol, Frenetic, On Point
Jazeter: Assault Rifle, Frenetic, Tuck`n`Roll, Infernal Tube, Sprinter, Nimble Fingers
Jazeter: Assault Rifle, Frenetic, Tuck`n`Roll, Enthusiastic, Unshakable, Unforgiving