Cyril, unfortunately your way may be a good way to work, but it doesn't cut it in most situations composers find themselves in these days. When the stems go to the dub, the mix should sound the same as if all were printed at the same time directly out of MIR. However, you can't do this, because it means that nothing can be changed if the film is re-cut, for example. These days we are expected to give the music editor options, and not providing stems is not an option for most people.
Having said that, I wouldn't provide more than 6 or 7 stems, but if each of these was a 5.1 configuration, that would saturate Logic's ability to cope really quickly.
However, as we don't have to worry about mic bleed or anything using MIR, it should not be a problem to create stems. All you have to watch for is that there is no processing on your Master buss in your project. All processing has to be done on the stem busses before printing.
DG