Hermu,
Unless you misstated your complaint, you were in error re: the map only responding to ext. MIDI devices. While the current drum map feature is less than worthless, as far as I'm concerned you can indeed use ANY sound resource you like. You just have to understand how to set the proper port, and then the proper MIDI channel.
For instance, I used to use drum sounds from my S'Tank library, along with sounds from my Alesis Fusion workstation, and even some from my Roland TD-8. So the way I would set that map up would be the following:
C3 C3 Studio Kick Ch.10 SampleTank 1 ... This is a VST.
C#3 C3 Funk Kick Ch.10 Alesis Fusion
D3 C3 Brush Kick Ch.10 Roland TD-8
Another tip from a VERY FRUSTRATED drummer/customer:
You might try making a bunch of smaller maps for each synth/VST that you have, and naming them for each drum part. For instance:
Make maps for all of your kicks, snares, toms, and maybe cymbals, and/or percussion for ABC Synth, then name it as such, like ABC Kick Map, ABC Snare Map. Then, do the same for your DEF Synth, and the same for GHI Synth. This way when you have to delete a synth out of the synth rack, you won't have to remember which note went to which port, or channel the next time you use that map. Since you named it after the synth, you don't have to remember anything, you just use choose the correct port from the dropdown menu. THIS is yet another feature the current drum map IS SCREAMING FOR that I learned how to work around, since they offer no means of printing the map!! What's also cool about this approach, is if you have a full 16 ch. VST synth, like S'Tank, or even Cakewalk TTS, you can load up ALL 16 ch.s (not just Ch. 10) with all of your fav, kits, or samples, then make your map(s) from that. If you need that particular synth to play other instruments, hopefully, your PC is hefty enough you can load another instance of that same synth. OR, maybe tolerate 2nd choice sounds from another synth, until you get all of your MIDI drums mixed, then you can open up another Sonar project file, import the mixed down WAV file of your drum mix, and proceed from there.
One final tip. You might consider adding your signature with all of your pertinent equip, and s'ware. This makes it like WAAY simpler for other users to help you since they can see kind of what you have, and make recs from there.
Other than that, it's just a Cakewalk...right? RIIIGHT!