Having a physical shield that prevents movement when being used seems a little odd. If one assumes relative motion then something that stops you using your engines could do that, but as far as static mass goes, it is just a matter of how much you have, not how you use it... But possessing a shield could certainly lower your speed and increase your energy usage, it would probably be a flat increase to HP, probably less than you would expect in order to account for shots that would get past it.
As for capturing, there is already stun weaponry, all we need is to shoot out the stun absorber and then jam the stun knife into their power-inlet...
A few basic statistic upgrading utilities could be handy for customising your suit:
Shield: +100 Hull, +1 energy used per tile moved. Effect cannot be deactivated without permanently discarding the utility, and then the quartermaster will kill you in your sleep...
Energy Field Stabiliser: +100 shield points.
Energy Shield Projector: +10 shield generation -5 energy per turn while activated.
Sensor Pod: +1 initiative.
Exhaust Jet: +5% evasion, +1 energy used per tile moved.
Drop Pod: +100 energy.
Experimental Control Unit: +50 reactor capacity, -100 power-down point.
Cargo Pod: two weapons' worth of ammunition.
Turret: +1 weapon with half ammunition or double energy use. Counts as a utility instead of a weapon for usage limits. -10 to all rolls the suit makes due to added strain on the suit's computer.
I won't even pretend that these are balanced...