Its not currently directly supported, mostly because in general the goal of the IK should be to get the hand to the non late updated position in the first place and secondarily because late updates are entirely useless then.
However I have it on my list of things to eventually get around to, being able to set an offset location to track instead that is, it would be useful for some specific features.
That being said, if you aren’t actually using them for hands, you can just use them for gripping components instead, there is actually an option to turn off tracking the motion controllers with them (for the FPS character). So you could totally attach “dumb” controllers to the hand mesh and they wouldn’t have the tracking additional overhead.
bool bUseWithoutTracking; will ignore the actual motion controllers location and skip all of the tracked device code, basically making it just a component that grips things.