Problem
Although the Alt or Super provide the necessary functionality, The key size and/or positioning can be problematic.
Solution
Offer the Space as a option, which can be reached from left and right and is easy to distinguish form the rest of the keys.
Limitation
- Currently there are bugs, caused from ignoring repeating keys in parts of the code.More specifically, the first repeat of Space(adding more spaces while kept pressed) stops some functions that were started with Space press. Most should be fixed with D12863, but I was not able to completely pinpoint this issue. The keymap item (I'm aware of) that will still have problem is view3d.view_center_pick, when used with Space, Alt and left mouse button key combination set.
- Keymap can be a bit finicky. E.g. ⇧-Space-left_mouse will first execute play animation and then pan the view. The correct order would be Space-⇧-left_mouse.
Alternative
Can add shortcuts in the default keymap, without the emulation part, but it makes the keymap code significant bigger and more complex. This solution requires D12855 too.
Although this patch works, D12855 would improve the usability. To prevent mixing keymaps, an often situation. E.g. shift-space and shift-space-left_mouse can be confusing as it is.
No talks, bug reports, or feature request. related to this patch exist that I know. This patch is more or less a feature request.