So I had a look at OpenVR2Key, I hadn't seen it before and I didn't realise it was open source. I setup my vive controller but thought I was going to have an issue as you said it needed an Index controller to map and he mentions that's what he has.
Ah, maybe I didn't make it clear, I was talking about Virtual Desktop when it came to remapping, it has a bindings page. OpenVR2Key works fine with my Vive controller/tracker even on the newest release.
I dug around a bit in the code and figured I could probably make mouse clicks work but would need to hijack some keyboard keys to test it quickly and not bother with the user interface side of that.
So I've mapped F1 to left mouse, F2 to right mouse and F3 to middle mouse.
I'm attaching my build of the exe and the source code.
But this is pretty handy anyway. The only issue is there's no repeating function which I think is a limitation of the program to begin with, if you hold a button down it only sends the input once, which means it's not very useful for games with machine guns. I found that by adjusting the click detection threshold to 1 (might not be necessary) and the dragging threshold to 10 in the Vive Mouse config, the trigger is a lot more responsive, there's no weird delay. You could probably go even lower than 10ms, I think the code just waits for whatever the dragging threshold is before it actually sends a click which is why it's so slow by default.
The other day I had demulshooter running with VD, but now I can't figure out how to get it to respond to clicks with vive mouse or VD anymore. Might have to restart and see if that fixes it, maybe the blocker stuff for vive mouse affected VD somehow, it might use user32 too to send fake mouse inputs to games. In testing I also think VD just responds better than vive mouse. Virtual Desktop is right in line, there's very little delay between moving the gun and the mouse following. With vive mouse it's like there's maybe a 50-100ms latency, if I waggle it back and forth I can see it lagging behind. I have stabilization in the config set to off and the average set to 1 in case that applies anyway, but it doesn't seem to make an impact. If it were possible to get Virtual Desktop to remember the last window position to essentially save the calibration, it'd just be superior.