today I have realized that, in Renoise, we can create MIDI CC events using a metadevice (MIDI Control Device), but we cannot create MIDI notes.
In my opinion it would be interesting to create a metadevice which allows this.
Such a device should have a slider for the velocity (00.7F), a slider for the note (00.7F), a slider for duration in lines (00.7F would be enough) and a swtich to actually trigger the note.
In what context do you mean that?
Why would we need a device to perform what the pattern already does?
If this is for effects, what is unsufficient about the current FxAlias solution?
it may be interesting to generate MIDI notes by manipulating other sources (Hydra sliders, LineInputDevice, a MIDI-mapped slider, and so on).
there is a whole kind of softwares, such as Native Instruments Reaktor and Plogue Bidule, which can do this, so why not Renoise; it just seemed natural to me that, since we can generate CC messages, we should also allow to generate notes.
…but wait… After all, we can already generate CC messages through patterns, so why would we need the MIDI Control Device at all? 
Because the pattern effects are limited to FFFF and the Midi Control Device is not bound to that limitation.
That is one obvious reason i can consider the Midi Control Device need.
I will have to sleep on this i guess.
or you have to look at the smiley at the end of the phrase 
well, anyway my proposal is of course not for people who are not into algorithmic composition or sound experimentation; I think that people who practice into this field could appreciate the idea. but I can actually be the only one, who knows
The field may not be wide, but you are definately not the only one.
Unstructured and improvised music generation can have its charming events.
Giving it a structure that makes it interesting to listen from start till end is the harder part about experimental music.
+1 for makenote