I believe the rustler should receive a HP upgrade too to be honest. When I chase the president in his 2000 HP vehicle it just takes 2 shooters who aren't completely clueless to shoot me down in <20 seconds...This is not really realistic as my 4 M4's should be much stronger then 2 M4's..
A bombing modification in rustler can prove a vital role in this regard. Since the guns are limited to area effect and range only, i would rather give prefrence to bombing runs made via rustler which can give an ability to the pilot to perform damage passes on the opponent similar or equal to the damage given by the nearest gernade against the player. Since most of the time presi or any other class player stays on the ground, this thing can turn the tables, both for the cops and terrorists.
About the bomb, once a bomb is dropped, he/she will have to wait atleast 30 seconds for the bomb to recharge and rearm for use. This can even save kamikaze situations.