If the Hercs are available as a platform then that can only be for one of 2 reasons;
1. The airframes are knackered and have no useful life left (without major overhaul) or
2. We can't afford to keep them in service.
Assuming that we are actually removing the Hercs from Service because of 2, why would we suddenly have the money to produce a lash-up using a palletised mission system (which doesn't exist in that sense - yes there are some MRA4 mission systems on pallets, that's a whole world away from a "palletised mission system")?
The capability has gone and it won't come back with half-arsed Frankensteinian attempts at resurrecting life from a dead corpse. It will take a lucid, coherent and, most importantly, properly funded strategy to begin to regain even a small part of the capability that has been unceremoniuosly dumped overboard.
Pulling My Yellow and Black handle tomorrow.