Ok, your target/focus project has been on my mind a lot so I'm going to do a sort of brain dump here on my thoughts and hope that some of it helps.

I think any system you design needs to be able to handle both character, mob, and NPC names, along with having a token based system. Token based system being that each character in your squad can be assigned one or more tags. Here are all the possibilities for tokens that i can see.

brain (character with a person in control)
healer (primary healer)
backup healer (backup healer)
cc (crowd control)
dps (primary dps)
dps lead (character that other toons use to aquire their dps targets)
slave (any slave character)
tank (tank)

First thoughts on token based focus and target passing. The token based system would be beneficial for pre-combat setups. I can see it as a great tool to simplify alt-tabbing between instances of wow and being able to focus more on a single window. I think that the tags should be able to be numbered so that you have dps1, dps2, cc1, cc2 so that you can distinguish between toons. Also some of this stuff could begin to be worked into a status window allowing you to reference which toons are marked with which tags.

It seems to me that this system would be the first step towards a system spoken of earlier (referenced as the perfect addon but i don't feel like digging up the link). Since Jamba can't pass targets or focus during combat, those options have to be hard coded into a macro before combat begins. I'm not sure what approach you have thought of for the system but here is my vision of it. I am not sure if all of this is doable from a coding standpoint but again, this is just a brain dump.

Jamba provides a completely seperate macro interface. All of your macros can be written and are stored inside of jamba. Macros can be written with token tags in place of targeting information. For example.

Your current party has a paladin named Tankadin who has been given the tag "Tank1"

/cast [target=tank1-target]

would be rewritten automatically to

/cast [target=Tankadin-target

I may have wandered a bit off subject but I needed to dump these ideas somewhere.