HI .
All the basic concepts you want to implement seem good.
However, I think they way you want achieve them may need to be adjusted slightly.
The game turn concept is sound,The basic action sets you want to use,I agree totally with.
However,I would prefer to use activation phases to break up the action rather than a separate list of reaction actions.EG use the game turn mechanic from Epic Space Marine.
This way the actions of the units are broken up into action types , and performed in a set order.And the action is book ended neatly by a start phase and an end phase.This gives more tactical loading at the start of turn, and allows more structure in the action sequences.And stops death star units having too much impact !
EG.
Command Phase.(Start of turn Phase.)
Players decide what actions the units are going to take , and place an order counter next to them face down.(Fire Support, Charge or Advance.)
Players request off table support.(Reserves, air/artillery support.)
Support fire phase
Units on Support Fire orders MAY fire before Charge and Advance actions are taken.OR after all Charge and Advance orders are taken.
Units on Support Fire orders make ranged attacks to full effect.May fire heavy /ordnance and max range on rapid fire.
Charge Phase.
Units on Charge orders must move up to double their movement rate.This is the ONLY way a unit may enter close combat.
Advance Phase.
Units on Advance orders may move and fire , or fire and move.Units on Advance orders may only fire weapons that are allowed to move and shoot.
Resolution Phase.(The tidy up before next game turn phase!)
Close combat may be resolved here ,to lock units in combat to give a bonus to assaulting units if needed.
Units morale is resolved with Rally tests, (if you want to include suppression etc,)
And off tabe support ( reserves, air/artillery support ) arrives now, and is resolved before the start of the next turn.
I only suggest this game turn because it worked really well for Epic
SM, which is about as large and diverse as 7th ed
40k is now!
Ill stop there , and let you comment on this variation of you basic idea.