Well just out of curiosity, if your node acts like a constraint then why is it not a constraint?
(i.e. some callbacks that would effectively re-route the setting of the transform attributes to set some
attributes on my connected node ( is this kind of cheating the DG?... is this bad?))
Is this bad? Well yes. To put it in perspective first you have to realize that connections are formalized callbacks, and there is no and should not be any reason you can not work your solution within those reference frames.
Failure to do so would brake the number one cardinal rule of programming (see coding horror: its your fault) and assuing you are right and everybody else is wrong. This leads to very horrific sets of problems. For one you now suddenly take on the task of maintaining everything everybody esle has ever done. And to be toatally honest theres only 2 situations where i recommend this:
your the kind of person thats hellbent on world domination, ready to take the consequences of your actions should your plan fizzle. (i suggest taking a few hours to look at the acrtoon pinky and the brain to rewally understand whats at stake. Remeber tough theres one difference between you and brain, he ia a labrat so his prospects for future are pretty abysmall as it happens yours are not)You have a lot of spare time on your hands.Secondly i dont really see any problem with achieveing what you want with a different design.
PS: one tidbit of maya knowlege it IS possible to expand the move tool by attaching more operantds in the super context (superCtx command which used to be documentred but is no more)