Rigging Talk

Switching in generic single space case like a parent space is pretty trivial - you getting the world space of the object you want to keep, doing the switch and then getting that world representation relative to its parent space. Roughly speaking: n` = n p^-1

What gets tricky is when objects have multiple switches i.e a position and rotation, as switching one could cause a pop in the other. The way i handle this is to essentially look at the resulting n` value and see if its offset is different for each switch i.e. its position is now changed even though its was a rotation switch and vice versa - then i set the keying.

I don't have add/delete targets but i'd see it as pretty trivial - you just re-populating an enum, and generating you constraints. I don't think that would be advisable during an animation. You need to store the targets, constraints etc or pull them through via listConnections, listRelatives etc.

Oh boy, a subject near and dear to me. The sane method is to use a script to match spaces on a single keyframe when you switch - however, that can still give a jerk, which has to be smoothed out. Additionally scripting can obviously be finicky about any number of different aspects of the rig, from hierarchy to naming.

I'm working on a method to have a seamless, smoothly blending switch contained within the rig itself, entirely within default maya nodes. It technically relies on creating a cycle, but you manipulate the node state to blocking such that the cycle never actually completes - you just save the offsets as a matrix within the blocked node, and use that as a startpoint to blend to a different space.

At the moment, I can do it with world-space translation alone, which comes to the next downside: it gets complex fast. I'm planning to present it once it can handle orient and parent constraint behaviour, but for me not having to rely on a script is definitely worth the slight hit to performance.