First my thanks to CNH for the material concerning liquid motor for Martel. This being the reason for a bit of necromancy.
On the basis of that material I think a liquid motor solves a lot of issues for System C.
Both by capability to throttle the motor between 100% and 10% and the ability to stop and restart the motor, especially pulsing operation, enabling lower total thrust in sustained flight and it's utility for manoeuvres.
Such a solution would permit System C to change course and recoup energy, throttle to ensure an optimal intercept trajectory and permit future increases in range/velocity through scaling up the propellant tank.
Making GAST.1210 achievable through the simpler expedient of more propellant.
Storage is reasonable for 5 years or more.
Fragility is no worse than a solid motor.
Initial thrust being the only cost and overcome by duration.
This would piggyback liquid Martel development as an affordable scaling of proven technology.
VL is still possible, though slower. Overcome-able by booster or internal accelerator in the silo.
Opposition is questionable since liquid Sparrow motor.....liquid Bullpup etc....
