[dotSILENT]

It's possible, I see that MTA did it but as far as I can see it's global, which makes sense. So one modification of weapon property is applied for every player.
I'm not sure about syncing the shoots then, don't know how samp does it under the hood but it probably wouldn't require any changing.

This plugin could evolve into some kind of all-in-one SAMP extension, but for that someone else would need to take it over. I don't have that much time, and I'm not the best at writing clean code when most of the things are experimental memory hacks.
IIRC wheel scaling could be easily added to this plugin as an additional handling option, it could make for some nice rim size modifications etc.
My main idea when creating this plugin was to create some sort of NFS-like upgrade packs for vehicles. You don't neccessarily need to set raw values. You can modify the existing ones, altering the handling.
In example, you can lower the mass by a percentage value and lower the drag multiplier, making the car go faster:

Code:

new Float:val;
GetVehicleHandling(vehicleid, HANDL_FMASS, val);
SetVehicleHandling(vehicleid, HANDL_FMASS, val*0.9); // 90% of previous mass
GetVehicleHandling(vehicleid, HANDL_FTURNMASS, val);
SetVehicleHandling(vehicleid, HANDL_FTURNMASS, val*0.9);
GetVehicleHandling(vehicleid, HANDL_FDRAGMULTIPLIER, val);
SetVehicleHandling(vehicleid, HANDL_FDRAGMULTIPLIER, val*0.9);

It's worth noting that subsequent calls to SetVehicleHandling wont create additional packets, since the modifications are all sent in a single packet at the next ProcessTick.