If you use RCBugFix, you will find a lot of people willing to jump in and help you. A lot of the developers are forward looking, and don't want to mess around with an older code base.
With that said... If you load up the RCBugFix branch, you can turn on Z-BabyStepping. That is very similar to what it sounds like you want to do. It uses the Encoder Wheel to Baby Step the various axis. But it would be almost trivial to have a button jog the Baby Step code one way and have another button jog it the other way.
With that said... If you load up the RCBugFix branch, you can turn on Z-BabyStepping. That is very similar to what it sounds like you want to do. It uses the Encoder Wheel to Baby Step the various axis. But it would be almost trivial to have a button jog the Baby Step code one way and have another button jog it the other way.