Changing saddle screws might have a tiny effect, but it wouldn't be audible. There's no one magic bullet. You can change the saddles- maybe a sonic difference, but it won't be anything other than subtle. You could change the entire bridge and there would be more of a change, but not huge. You could then change the nut to brass and maybe you might notice a wee change. How about a new neck made from magic tone woods?
Perhaps the change you are looking for is a new bass. At some point the economics of modification are sketchy at best. Not that you shouldn't try some mods. Go ahead - it's only money.
This is not aimed at the OP, or anyone else in particular. I've just seen too many clients that were pursuing the sound in their head by doing mod after mod on their instrument, only to become so disatisfied that they ended selling at a loss. Maybe the best course of action is to stop listening to that sound in your head.