I totally agree with your accessment of the percussion. I grew up with deep percussion, my first band featured a rhythm section with Timbales and Conga (initially no trap kit). My first visit to Yamaha back in 1986 I demo'ed a set of sounds I edited in the RX5 that added the various "left hand" articulations involved in playing congas. I think it had a lot to do with me getting hired later.

The thing about any synth engine, you can edit. Those folks who didn't grow up with such percussion instruments wind up sampling just what the GENERAL MIDI drum template outlines... which you know, is incomplete. (I used to call it the one handed conga player, because it was all right hand sound, no heel/tip of the left hand. To me it was as empty as listening to a snare drum played on just the "two" and "four" without any ghost notes in between (I never met a drummer who could just hit 2 and 4, without the bouncing of the stick. And it's those ghosted Snare ruffs that make it real.

You can take many of the sounds provided and edit them into some nice alternate percussion sounds.
You can load data as new Waveforms to your instrument.

I'm quite sure in the past decade of Motif there are collections of detailed conga, timbale, and other hand and stick percussion sounds.
We all want the sounds we are into to be covered in greater detail. The GM drum map gives you hi bongo, lo bongo, period. Conga, you get slap, hi open, lo open (all right hand sounds)... I'm sure you know what I'm talking about.

We have folks around Yamaha who know this stuff and have the skills to translate it to the technology, but to get to where this kind of stuff is standard takes time and development and therefore, must be supported by market interest.

The only troubling thing about your request is that you put no value on them. One of the ongoing discussions when developing content is the one that has the Wave ROM having to cover all these different musical areas... and then, how deeply do you go into each area, how deeply *can* you go into an area and still cover all bases you need to cover. There is no perfect mix... the best we can offer is what you get, PLUS the ability create your own custom WAVE ROM. The concept of the Flash is that *you* get to choose the data that populates your Flash ROM. A good portion of the instrument is user customizable precisely because we cannot cover every area of music as in depth as it deserves -given the wide variety of music genres in the world..

But this percussion thing is an area of interest to many of the users that I talk with and is on my list of "things to do". I know exactly what you are talking about... but appreciate that what I assemble will not just be the "free" stuff. If it is musically important to you, it should be worth something. Those sound designers who have the skill and knowledge to bring usable in depth sound libraries to market deserve to not have to just giveaway their work. If you understand that not every category can be covered in depth... then a targeted library should be worth something.

Extra Credit: there are a lot of different hand drum samples in the MONTAGE, these can be edited and fashioned into all kinds of articulations.
Recording your own and importing them to a MONTAGE drum kit is also a viable option.