P2 = you are physically fit, can pass all fitness tests, work within physically demanding limits
FE = forward everywhere, you are a fully deployable individual
P3 = you are physically fit, but within limits as dictated by your UMO with regards to specific injuries and illnesses.
You should have a Light Duties Proforma - a 'biff chit' to exclude you from any physical exertions that may exasserbate your illness/injury.
Calfes - you should be excused CFTs PT ect.
LE = you may still deploy, but not front line, but to the limits of 'lines of communications everywhere (LE)'.
downgrading you for a short period would help you
1. overcome an injury or illness
2. prevent further injury / worsening of you condition
3. protect you whilst under review or treatment.
(stops the army breaking you further!)