The Resistance lacks the resources to develop the weapon, but will probably go through the motions of acting like they are to force the FO to deploy like they have it in the field. Additionally the FO has NO REASON to develop a super capital ship killing space missile themselves because it invalidates their entire fleet doctrine. If the FO is competently run, this new weapon is utterly useless against them. The shields only need to remain at power briefly, milliseconds actually, and then those ships need to be brought out to the specific range to deploy them against larger capital ships. The Resistance has to develop a smaller weapon that is probably around Y-Wing sized that has these shields and a working hyperdrive. This is super easy for them to do and requires only a redeployment of other assets presumably. Possibly they may employ interdictor technology on all of their capital ships going forward if the Resistance can lock this weapon down going forwards. The FO, if they have ANY sense will begin working on a counter to this, which will probably be little more than an interdictor class ship to accompany their larger capital ships. Now, with current technological development in universe, I expect two things to happen. Without the shields, the maneuver doesn't work, and as those shields didn't exist prior to TLJ, it was not possible to be utilized earlier than that. You are going to have to build a weapon capable of utilizing these shields, briefly, while also powering a hyperdrive. Weaponizing this is going to be tricky as the shields were essentially mounted to a purpose built heavy cruiser and required extreme amounts of power to operate. These new shields could survive, briefly, the destruction of their ship and continue their projection down range for a few milliseconds which at light speed translates to a considerable amount of distance covered. So Apparently the Raddus was utilizing a new type of shields that were different than previous shields.

Hyperspace ramming