I suspect you want mods to do all the work lol..but why? Let the admin+theme do all that.
There has to be a middle ground, of reasonably rigid definition, that both sides can reasonably expect to be present. Turning it on one side so that one side has all the power, it hamstrings the potential of the other.
SMF put too much power in the modder's hands, what you're suggesting removes most of the power they would actually have. I want a middle ground where I can write code that I have a reasonable expectation of being supported the way I want it to be, not some vague notion of support.
Also, if anything, it's actually making life a lot harder for themers to do anything creative. Because I guarantee you that if themers are given totally free reign, people will have trouble using add-ons because they just won't work as expected. Take a look at WordPress sometime and how many people really do have trouble with Widgets - and how many themes actively state what they support for just that reason: because they give an awful lot of flexibility to the themer and little to the modder in any real sense.
Having some semblance of structure ensures that both sides have a reasonable expectation of things working.


