To the point of separating out the module from the keybed itself, I recently bought an Ensoniq TS-10 precisely for that very purpose (controller keyboard with poly aftertouch) - and, happily, it's wholly flat on top, perfect for desktop modules:
Also - the most alluring thing about its feel is the contactless keyboard, which requires very little downward force to engage. Imagine the long*-throw Fatar keybed from the Waldorf Wave / Kawai K5000 without the bubble contact weirdness....
I did not think that I would enjoy this as much as I do, having been used to positive-action keybeds (such as a tracker organ action, or my DX7), but it seems to fit the bill and it's forced me to revisit playing technique that, frankly, the Fatar and CME keybeds just could not accommodate (think Pratt-Read J-wire, as used on the OB-*, Arp Omni, etc., without the initial bit of pressure). And Ensoniqs are cheap these days.
* relative to the shorter synth-action keybeds, anyway
(Strangely, this post ended up in another thread - think the forum frameworks are having a "day")