No bass without an active/passive switch can be used live and even that is questionable. It should be a battery powered active switch with a capacitor that makes a smooth transition to passive mode when power goes down. You need a "battery low" blinking dot on the side of the fingerboard to tell you not to go on a long solo right now.
The most common gauges used for passive bass guitars are 18 and 22. Next, you need to take into account the type of pickups you are using. If you are using passive pickups, then you will need to wire them in parallel. However, if you are using active pickups, then you will need to wire them in series. Finally, you need to consider the number of
This has probably been raised a bunch of times here, but what's your take on a passive bass with a eq pedal or rack as opposed to an active bass with a built in eq. The reason I bring it up is I love the flexibility of modern eq's but I'm a sucker for old school passive jazz basses.
I would personally recommend one of the passive G&L's to stock with flats. I have an SB-2 and it sounds really great with flats on it. Their other passive models are the LB-100 and SB-1 which are Precision style basses and the new JB-2 is the their passive Jazz type bass. Here's a shot of a G&L LB-100. That's a bass that sounds really sweet