Dynamic shortcut system (similar to Dynamic Shortcuts in Gimp, but also applying to tools, paintops and presets)
Shift drag sensors
Currently shift+dragging the left mouse button horizontally can be used to alter the brush size. This is awesome as it minimises time wasted going back and forward between where you're painting and the brush editor a million times. It would be even better if brush softness, hue, value, page zoom etc could be changed in a similar way. Shift + drag could be used with any othe three mouse/stylus buttons (left - LMB, middle - MMB, and right - RMB click) both horizontally and vertically, giving us up to 6 things that could be quickly changed, right at the users cursor. This proposal is to make a system to link any of these shift+drag options to modify brush properties or page zooming in a fast, intuitive manner. For example shift + vertical LMB drag could modify brush softness, shift+rmb horizontal drag could be assigned to changing opacity, shift + mmb horizontal could be assigned to modifying brush hue, shift + mmb + vertical drag could be assigned to adjusting brush value and so on. Possibly these could be implemented as sensors and thus assigned to anything in a brush that currently has a curve. The only problem with this approach would be that I would really love zooming on the canvas to be possible with this too. Yes we have mouse scroll wheel for this, however that's not available on many tablet styluses (like mine ;P )
3D Material Image Maps
3D materials are made up of a bunch of images called image maps. If the user could associate layers as image maps in Krita, and paint on all of them at the same time, artists could paint whole 3D materials - something currently only available in high end 3d apps like zBrush (not even Photoshop / Corel Painter). The trick is that the position of what's painted needs to match on every map/layer, but the colours vary. For example, a scratch on a human characters skin would have a red colour map, a white (=raised) bump map, a light grey (=semi-shiny) specularity map etc, all in the exact same location on the each image map. Traditional methods of trying to create each image from scratch or by manipulating the colour map are very, very slow and painful. A simple version of this could be done as follows:
1. Each layer has a toggle in the layers docker called "texture map" or similar. This is turned off by default. When active, the brush paints on *all* layers that currently have "texture map" active.
2. When picking a colour, a dropdown lets the user pick "Default" or any active texture map layer. "Default" is just the current behaviour. If the user selects a layer in the dropdown, then the selected colour will be applied to that layer when painting on *any* layer.
3. In the file or layer menu is an option "Export texture maps" which saves each texture map layer as an image. The layer name and extension appended automatically to the file name. For example, on a file called character.kra, the layer titled "colour" would be saved as "character-colour.jpg" (or whatever format was selected).
For step 3, a simple, one click / shortcut, method is vital, as artists often have to check their material in their 3d app every few minutes, and wading through saving 10 layers individually, each with manual file naming and confirming file format settings each time is unacceptably slow. For any artist who requires this level of control, they can use Layers menu -> "Save Layer as Image" already in krita.
Allowing artists to paint a single material rather than creating multiple separate image maps by hand, would make Krita formidable for painting 3D textures, and the most advanced open source application for 3D texturing.