Love using a swipe to move and resize windows to left and right halves. Have been developing app specific, always on, palettes using Keyboard Maestro.
Some actions that are common to most apps like closing the focused window or hiding the app, are shared by most palettes leading to the idea of having a global palette stretching across 2/3 the top of the screen as a sort of always on custom menubar with a second app specific custom menubar occupying the remaining 1/3.
Here’s the request/tie-in, allow the predefined Maximize Window Right or Left Action be editable as are the custom Snap Areas.
This could be via a dialog box with fields for window size and location settings or perhaps have the settings for the Snap Areas have an option to used as presets.
What I would do with this is edit the Maximize Window Right or Left Action to leave 80 points at the top of the screen empty for my palettes. I’d do the same for the Quarter resizes as well.
If there is a way to do this with AppleScripts maybe you could post a sample for me to work with?
btw, Keyboard Maestro has a wonderful way to move and resize windows but doesn’t have BTT’s far better trackpad gestures. Ya’ll really would benefit each other and us if you more fully integrated. Just saying 
Thanks!