I would think it would be easier and more efficient to just make a really powerful powered exoskelengton than to mess with your mass.
Exoskelingtons are not logically agile.
Agility is badass.
Ergo:
Greater strength allows for faster and more vertical mobility. The rest is just manual dexterity, which is up to the operator anyway.
You'd go Up faster, sure, but also down.
Plus the power v weight ratio would have to be really high or you'd be going in circles.
As for "faster and more vertical mobility", making yourself weightless for a half-second would do the same too, and then you could safely land on a weathervane, or pidgeon.
Make you weigh more, but remember:
1) The servos could be used to reduce movement as well as increase it. Lower your arms and the servos, rather than ceasing to function, could function at a reduced rate allowing more finesse.
2) You'll accelerate down towards the planet you're on at the same rate. You'll have a higher terminal velocity and when you land it would be akin to FO 4's power armour landings (ie a loud smack, not a quiet one), but if you have exosuits then you probably have shock absorbers in the setting
3) I had a 3 and forgot it whilst I was writing 1 and 2
You'd also want a strong frame for when you turn the weight reducers off, or they get damaged in combat. If you can still move when they're not active, that's much better to take into dangerous situations.
Again, though, we have tech for a full fledged combat-capable exo suit. We can probably assume the material technology is pretty good compared to modern day. Heck, it might even be a pretty light exo suit if the material is made out of, say, carbon instead of metal.
The whole point of that little discussion was Tack talking about how you could afford to make a very heavy armoured suit and reduce the weight until it was usable. As such, we can assume it is made out of heavy materials.
That makes it more fun because THEN you can basically run around in tactical dreadnought armour. (I don't remember the name for those super heavy spess mahreens guys)
If it's heavy and there's a lot of materials advances, though, then the thing's gonna be pretty hard to crack. If you provide enough force TO crack the armour, then you'll probably kill the guy inside simply because their body can't take the force.
Sorry Gigla, the idea is awesome but the argument was actually Exoskeletons VS Gravity-reduced-battleplate.
But I've gotta say, having both sounds pretty sweet. Here comes super-agile terminators.
Sadly no matter how much your gravity is reduced, you're still looking at hard landings 'cos inertia.
You could use gravity dampeners to reduce your fall to a brisk walking pace but when you hit the ground, you're X heavier than usual, so it'll still be rough on the knees.
Fucking physics.
Edit:ed for clarity and quote pyramid.