What you say here sounds just like my thermal interpretation: Each measurement result is macroscopic, hence a property of the state of the measurement device at the time of measurement.I don't understand that statement at all. There is no additional interpretation involved. This view simply says that quantum mechanics is a way of predicting probabilities for macroscopic states. There is no additional assumption about measurements.
What I'm claiming is that the result of a measurement is always macroscopic. You produce a pointer pointing in one direction or another. You have a visible dot on a photographic plate. You have a click on a Geiger counter. These are all simply macroscopic facts about the world. There is no need to make a distinction between measurement results and other kinds of macroscopic facts.
But which property should it be if the measurement device is described by quantum mechanics (and hence, according to MWI, only by a wave function)? Clearly, this property must be a function of the wave functtion (the only thing that exists in MWI). But what to call measurement result is left unanswered by MWI and requires another interpretation.
You give no mechanism that makes the macroscopic state behave such that measurement is possible - i.e., that it correctly reflects in the measurement apparatus a property of the microscopic state of the measured system. You need to postulate (and this is the extra interpretive step) that the macroscopic state is a classical probabilistic state, and you need to justify why the observed (objective) frequencies, measured on individual systems with their individual states produce the correct probabilities. MWI doesn't do this. It gets (like shut-up-and-calculate) a probablility distribution by Born's rule, but...
It does not justify why this probability distribution is actually observable as relative frequency in the single world experimentally accessible to our culture. Splitting wor(l)ds does not help the least for that!
This current dilemma is called the measurement problem. Only tying things down can ever resolve it.I think that's true with every interpretation. None of them really tie things down.
No worlds ever emerge - otherwise there would have to be a dynamics specifying how they emerge. The emergence is only in the head of the believer.of the emergent worlds