So in LCPDFR, I had to disable hardcore mode because if I was shot at during a traffic stop I had no chance of returning fire before I was dead.

So I thought it would be good if in LSPDFR, which I assume is more advanced and supports more stuff, when shot upon in a traffic stop the officer automatically pulled out a gun to assist the player.

I understand where you are coming from and that is an idea but that is obviously not for everyone as it takes away a realistic situation. Also right now LSPDFR does not have a hardcore mode, I know there are health mods to edit the level but LSPDFR itself does not have a hardcore mode like LCPDFR nor do drivers ever pull weapons while in the vehicle as of right now unless they get out of the vehicle(at least I haven't ever had one do so yet). 

The game already slows down when you change/equip weapons so that should make up for it

I can see why you'd want this but it can take away the adrenaline-rush from the scenario. But like simulator said I haven't had a driver shoot me when hes still in the car.

Advice: Remap the keys so that "draw pistol" is on the mouse. I have it as middle mouse button, which solves this issue neatly.