I imagine registration missions would be pretty closely tied to posture anyways - So a registration mission would allow a unit to get TRP/Preregistration, the number of which would then be determined by posture (as it took time to conduct pre-registration fires, etc). I imagine the way soft factors would affect this is by adjusting the speed at which a unit increases its defensive posture?
There is nothing wrong with the attacker in a scenario having no registration, I've no idea how historical it was, especially considering counter-battery fires, but if we are denying TRPs to attackers, then we need to make some minor shifts.
Right now, pre-registration does a few things for you in ASL. It makes battery access easier, it vastly increases the accuracy of spotting rounds, and allows one to call a fire-for effect without having to first place a spotting round at all, if one wishes. It also allows the use of barrages (A linear OBA mission, essentially) and creeping barrages. These are only allowed if the attacker has a pre-registered hex, so if we are not allowing these for engagement attackers, we might need to have a mechanism in TO that would allow an attacker to set this up. Or we could just say no barrages allowed for the attacker, although that would deny the attacker some interesting options for laying down smoke curtains and such.
There is also a bombardment mechanism, where most of the map gets attacked by a 2 morale check before the battle kicks off. I have chosen to represent this by the following:
3.12 PRE-SCENARIO BOMBARDMENT:
A TO engagement preceded within a two-hour period by a bombardment from an artillery battery or batteries of over 100mm that fire(s) an Area Fire or Bombardment mission, or any Specific Target or Air Bombardment mission, may cause damage to defender fortifications and the map terrain. Note that damage to defending units due to pre-engagement bombardment is already calculated by TO, so only terrain/fortifications can be damaged in this step. Once the scenario defender has completed setup, but prior to the scenario attacker doing so, a bombardment is conducted per C1.8, except that only terrain and fortifications are affected. In addition, any fortification counter not addressed in C1.822 (EX: Trench, Foxhole, Sangar, Panji) if in a bombardment hex is is attacked with a ML of 9. Any unit in a hex in which terrain/fortifications are damaged/eliminated is unaffected, but may be re-setup as desired by the defender, and will retain/gain concealment if able to do so as normal prior to attacker setup. If the bombardment is conducted by an artillery battery ≤ 155mm, and/or by an aerial bombardment conducted by a bomber unit, then all terrain/fortification MC are at -1.
Long story short, the bombardment happens in TO, the unit is affected by it there and in the force generation process as per, and then the terrain gets attacked to represent the bombardment. This has nothing to do with pre-registration, btw, just another thing that the system can do.
Barrages are what I now need to tweak though, and why I need to know how this would be handled in TO.