But why bother... if you want a Kubicki then you want an ex-factor.
Not sure I'd agree with that... The fiver seemed to me like a decent compromise of the (Ex-)Factor's ergonomics to fit five strings. A headless five would have been even nicer but I can get that committing to a five string version of their tuning bridge would require a whole lot more sales than Kubicki could reasonably expect.
(edit: On thinking about it, the tuning bridge shifts the picking and fretting areas pretty far to the left. Not that big a deal on 32" scale, but probably an issue on 34". Maybe it was better the way it was.)
I have previously owned Ex Factors (a black '89 and a Bahama-green '94) and currently own a an '89 fretless Factor (34" scale and no string clasp mechanism). Ex Factor and Factor basses are in almost every way identical, including the shape and length of their necks. The only differences are the presence/absence of the string clasp mechanism and the placement of the nut.
There are many, many reasons, as Scott observed, for wishing to own a Kubicki bass beyond the cool low-E to D feature on the Ex Factor. In fact, despite my prior great experiences with Ex Factors, since I wanted a fretless, I specifically searched around until I found a Factor model due to the slightly greater ease of playing a fretless with acceptable intonation when it has a full (rather than short or medium) scale length.
Now, would I convert an Ex Factor to a Factor, or vice-versa? No chance! Both are impeccably constructed, incredible sounding, and superior playing instruments just as they are and there are too few of them out there, I think, to mess with them. Better to wait to find the one that suits your needs/preferences best and enjoy it as it is.
I can confirm Scott's observation that, due to the tuning mechanism on the other side of the bridge, the relative position of the neck is shifted to the left when holding the bass in a standard playing position. I find ardgedee's description of it as "pretty far" to be misleading, though. In comparison with a P or J bass, it's only perhaps by an inch--a couple at the most, In any case, I'm 5'11" with proportionate arms and find reaching the far end of the fingerboard perfectly comfortable. Perhaps players with more limited reach might need to consider that, however.