CSI is in fact not so difficult to understand and it is quite flexible. I mean you can create a preset similar to your current AZ Controller preset.
OSCII-bot works with MIDI and OSC. It can communicated with REAPER throw OSC (bi-directionally), so people which don't want/know C++ programming
write MIDI communication in EEL2 as OSCII-bot script.
Writing AZ Controller in EEL2 is like playing drums with e-guitar... You can use audio2midi plug-in and then map midi notes to drum kit peaces. So, possible.
But there are better approaches to play drums
CSI (as REAPER and all its extensions) are written in C++. Justin has claimed it is not possible write GCC compiled REAPER add-ons.
Well... "NotA" extension and "ReaCWP" are written in plain C, cross compiled under Linux with GCC.
Noel has thought exporting Cakewalk projects is not possible without internal knowledge (someone before me has even tried, without success), yet ReaCWP is the first (and for the moment the only) cross-DAW project converter
.
I mean many things are possible, but hard to implement. Some of these "hard to do" things have a good reason to exist. At the same time, if something is hard to do that does not mean it should be implemented