I wonder if it would be possible for each IFV to have 2 crew and 9 dismounts?
Not sure on the layout and workload of the turrets concerned but I assume the gunner and commander both have access to all systems and can operate the turret on their own? Could it potentially be possible for the gunner to be the vehicle commander (say an experienced Boxer commander) to be RAAC with the dismount commander (and section 2IC) being RAINF but either taking the other seat in the turret? Not ideal but the battalion retains the capability of deploying at full strength, dismounted and the vehicle is still mostly effective without the dismounts. Turret operations could be introduced to corporal subject courses, with the knowledge they will have an experienced RAAC NCO sitting next to them in the turret.
Perhaps the introduction of SPGs will free up enough manpower to cover the increased numbers required to introduce the IFVs?
Just an observation, I have noticed RAAF integrate very well with air RAEME, infact there is less "them and us" between RAAF and RAEME airtrades than there is between air RAEME and ground RAEME. It seems the common work environment and working on the same gear with the same systems leads to better comradery and greater effectiveness than being in the same corps. People living and working together, operating the same equipment, and training to fight together should do ok.
Another thought is, again manpower permitting, infantry and even RAE could provide assault troops to the ACRs to back fill the numbers seconded to crew IFVs and future armoured engineering capabilities. Again, like the seconded RAAC personnel, these would be senior and experienced soldiers in their ECN, able to pull their weight in a new and unfamiliar environment. Detachment commanders would ideally also be from the lending corps and senior in their rank. I would imagine assault troop platoon commander being RAINF or RAE, while each Btn could even have a Rec Platoon crewed and commanded entirely by RAAC (former US National Security Advisor and ACR legend, HR McMaster, started his career as an armoured infantry battalion cav platoon commander).
If this is done properly individual soldiers will not be overloaded with training and excessive proficiencies, but will become very effective at working in combined arms, while excelling in their own professions. In the long term, virtually every senior NCO and officer in each RAAC, RAINF and RAE battalion and regiment, will have served on secondment to one or both other corps during their career. The potential of this could be transformational.