How about taking flight idle's ng , Tq, and t4 right before takoff as FLI=0 (or 1 if you prefer)
and interpolate between this and max. continous?
The interesing part is the gradual reduction of the margin to "max. allowed FLI" while operating in the higher than continuous area,
especially when having "used" 4 mins. of some "max 5. mins limit" a reduction of power demand to below max. continuous for 3 seconds probably should not allow another 5 mins. of over max. continous power.
That is you need to model a "cool off" phase for each transient limit and all possible combinations thereof
which only when fully achieved enables another run of the "5 mins. limit",
but when that cool off phase was shorted the "5 mins." limit would become a "2 mins. limit"
P.