I'm pretty sure a good few of you guys here are familiar with the anime Infinite Stratos, never got around to watching the second season as I got bored of it, and I'm not advocating to invent one, but why not use the idea behind it? Add an outer armor layer with extra arc-reactors, more powerful and over sized repulsor-based thrusters specifically calibrated for speed add in a few vehicle based Kinetic Barriers, vehicle based Weapons and such to help protect its wearer, allowing the suit (dunno if ours are airtight yet and didn't feel like looking it up but I suspect they are) to essentially be used in space as (makeshift) fighters, for boarding actions or maybe even orbital re-entry with its vehicle based barriers. May even be quite easy for our people to boost up into orbit, run a sub orbital flight path and drop somewhere else on planet not long after, dunno the time scales but it would allow long distance (jumps, if you will) easy.
This part of outer armor would be easily detachable in cases of emergency or damage or if their is plainly not enough space for it. In case of detaching it, you still have the standard armor and weapons underneath it (might need to sacrifice any type of shoulder mounts though to use those connection points to the outer armor), yet would add a shit load of (fire and shield) power to each and every armor we can field along with the fact that each type of outer armor we make can be easily made modular to adapt its weapons to the mission, or just make several types (close-mid-long-artillery and even a medical support version carrying extra supplies could be done) for whatever setup you need.
I see a couple problems with this, and it's similar to why super-versatile mechs are not worth it.
It basically boils down to the fact that specialized equipment is usually better at its assigned role than all-purpose equipment. Lot of reasons for that, ranging from optimization (e.g. pure fighters are far more optimized to their role than makeshift fighters) to training (e.g. you don't want infantry to try flying planes). AND if you need flexibility, well that's what the variety of units among fleets and armies and combined arms are for.
The only use case I can see is for units that do require maximum flexibility, that is, elite special forces.
Even then, there are other problems with this outer armor that limit this use case, and they have to do with the size and bulk of this "outer armor". The size of a "foot soldier" (infantry or special forces combatant) is useful because they can partake in combat in practically all habitable areas. If the outer armor is sufficiently large enough, it can limit the terrain the infantry can take action. Furthermore, where are they going to keep the outer armor, if they have to disconnect it in the battlefield? It's not like some handheld weaponry that you can just strap to your back, and this outer armor surely is expensive enough to not be expendable.
Also, power suits already include some of the capabilities you're describing, including flight (with mark 2+ and repulsors) and extensible mounts for whatever specific functionality you require, albeit not to the scale of your suggested outer armor. For ex, that "Kasa Guardian Angel" system that UberJJK just referenced in the previous page.
Of course, this analysis presumes no Reaper War in a decade or so.
I'm all in favor of taking advantage of logistical weaknesses in Batarian territory, but even ignoring the Reapers, I doubt we'll have the time to drag on a war or occupation for decades, let alone trying to force Batarian society to change without occupation. At that time scale, political challenges will crop up, from the expected war weariness back at home, to skittishness from the Citadel Council and Terminus powers trying to preserve the delicate status quo.
I think the best strategy is to take advantage of the SA/PI's tech advantage and comparable industry and wage war with conventional strategies. Tactics might change due to the new tech, but the standard overarching strategy of defeating fleets, achieving orbital superiority, and
invading liberating planets is still sound. As long as the SA is waging war successfully and freeing slaves at a rapid enough pace, we can sustain political will both at home and at the Council.
If Collectors or other Reaper influence interfere in the war, I have the confidence that either: a) SA/PI will be able to overcome it; and/or b) the Council and rest of the galaxy will realize the threat of...something at least very ominous (if Reapers haven't been identified yet).
When it comes to actually invading Batarian inner worlds and Khar'shan, that will be trickier. Again, because of political reasons rather than just military ones: what the hell are SA and the Council going to do with a defeated and occupied Batarian Hegemony? SA lacks the manpower for long-term occupation over the breadth of former Batarian territory, while the Council doesn't want the young SA to suddenly rival major powers in terms of territory (or at least claimed territory). Furthermore, a UN-style occupation force might not be an option, because the Terminus powers could raise a fuss.