I only just now saw this discussion thread, so my contribution might be a bit belated and I don't know if it will help.
I do not use a proper mouse. I was an early Apple Mac user in the '80s, and learned to use a mouse then. However, I now use only Intel X86-based PCs and I favour keyboard navigation over mouse navigation, but the mouse is essential on the modern Windows GUI. I forcibly trained myself to use a pressure-sensitive motion lever, and then a touchpad mouse on my laptops years ago, and would now rather use the touchpad as it is ergonomically superior and far easier to use compared to either a motion lever or a conventional mouse (better ergonomics and especially no RSI). My current Toshiba laptop has a Synaptics PS/2 port touch pad. The software is version 6.2, and is full-featured, offering many useful options including:
(a) Constrained motion: You use this to enable a vertical/horizontal plane lock for the pointer. You can select which of the various keys or key combinations you want to activate it with, and I selected the Shift key. The lock is enabled by pressing and holding down the Shift key before you start a moving the pointer. The plane is then locked in whatever plane approximates vertical or horizontal where you first start moving the pointer, and stays that way for as long as you keep the Shift key depressed. This is quite a handy feature, and is very easy to use.
(b) Slow motion: To select slow pointer for precision pointing. You can select which of the various keys or key combinations you want to activate it with, and I selected the Ctrl key. Slow motion is enabled by pressing and holding down the Ctrl key, effective immediately (whether you are moving the pointer or not) and is then locked for as long as the Ctrl key is kept depressed. I set the pointer on my laptop to accelerate and move at "fastest" speed normally, so as to be able to navigate across the screen as quickly as possible. Even though the pointer is usually pretty accurate when moving it at speed, I very occasionally may need to use slow motion when the pixel-sensing area for an object is small. This too is quite a handy feature, and is very easy to use.
These are the sorts of features that you might need per this discussion. If it was tricky to emulate them using AHK, then I wondered: if you have a PS/2 port connected mouse or pen, then might it be worthwhile experimenting by installing the Synaptics PS/2 port touch pad drivers, to see if these features would work for those devices too? I know it works for non-Synaptics touchpads where the Synaptics touchpad drivers are not part of the OEM installation (because I have tried it), so I presume it is using standard port connections at the PS/2 interface.