Mike, I think you have got something fundamentally wrong.

As I understand it, you CAN'T use a 'loop kit' to play a MIDI file, only the regular kind of drumkits same as you have in your current arranger...

There are no 'loop kits'. A loop is just that... a recording of a drummer playing a groove, all the sounds mixed up one ONE stereo file. There are going to be hihat hits or ride hits on every single beat, at the same time as snare and kick. You can't separate them out, or send a MIDI note to just one sound.

Now, if I were Ketron, I might have used the kit that the drummer played to make a regular MIDI drum kit sample set, to allow you to modify or replace the loop with minimal timbral change, but no word has been said about this possibility, so I don't have high hopes for this.

The thing that bugs me is that, if you listen to the better drum kit libraries that modern computers can play, EZ Drummer, DFH Superior, BFD, etc., and the MIDI grooves they develop for them, played by real drummers on MIDI drumkits, you can hear that even without going to live loops, you can get drum realism that is amazingly real, amazingly live, and VERY hard to tell it ISN'T a loop...

But with NONE of the loops disadvantages. No editing, no changing kits, or drums within the kit, no changing the 'swing factor' on the style, etc., etc.. It strikes me that, were enough ROM dedicated to a kit with this level of detail and dynamics, you wouldn't NEED loops. ROM memory is a fraction of it's cost from just a few years ago. Surely this is the better, more flexible solution without any drawbacks?

Give these a listen: http://www.toontrack.com/ezdrummer.asp (check out the expansion packs, especially the jazz drums, the Latin Percussion, the Nashville brush and rods kits, and my favorite, the Twisted kit!
http://www.toontrack.com/ny_legacy_vol2.asp
http://www.fxpansion.com/index.php?page=53&tab=148

Bear in mind that most of the demos are geared more to the younger player/producer, but there ARE some for us old farts mixed in..!

I happen to feel that loop technology for drums is a dead end, unless you NEVER mess with your arranger's drums at all. And how many of us have NEVER tried a pattern out with brushes instead of sticks, or turned down (or up!) the reverb, simple basic things like that that you CAN'T do with loops.

I really hope that arrangers don't go down that path wholesale, and reduce us to playing preset patterns whether we like them or not...