Is it possible to reverse cable direction in Shimano M770 shifter? I tried to set up the perfect shifter + derailleur. For the last part it is better (for me) to have low-normal version, because reducing gears is essential for me (I bike mostly within city).

So I bought low-normal Shimano derailleur (Shimano-RD M770 SGS XT) and M770 shifter. To my surprise it is asymmetric shifter -- you are able to release gears by 4, and increase by 1 (I tuned M770 already, so I am able to increase gears by 2, just like with XTR).

So with current configuration I can more easily increase gears (by 4) than reduce them -- quite contrary what I wanted.

I can send back derailleur, and order a new one, with top-normal spring, but I would LOVE to improve M770 shifter even further by reversing the direction of cable, i.e. so the thumb level would pull the cable, and index level would release cable.

Such tweaking would result in dream machine (well, part of it).

The question is -- is such modification is possible at all (at home)? I would appreciate firm "no" or "yes" (+how to do it) answers. Thank you very much in advance.
You should switch your derailleur out for one with a reverse pull, but there is absolutely no chance that you'll get the shifter to reverse the operation of the cable.