For me, the only way to upgrade that bridge would be to get one that is quick release for ease of changing strings. Something like one of these:
Hipshot Vintage 4 String Bridge String Through - Best Bass Gear
Hipshot 4 String A Style Bass Bridge - Best Bass Gear
Hipshot Vintage 4 String Bridge String Through - Best Bass Gear
Hipshot 4 String A Style Bass Bridge - Best Bass Gear