There are absolutely no mistakes made on that bass. Not one.
Why does it work? Well, one part of the secret is the neck through design combined with dense neck woods (purpleheart added to the maple) and probably a fairly substantial brass bridge block.
Whatever strings are on there could be part of the magic formula for you as well, so be careful about trying different things.
As far as the spacing goes, those basses are super fast and playable as long as you aren't planning on playing a lot of slap. The spacing is a bit snug if that's your goal, but straight finger or pick playing is a breeze. If you want to try narrow spacing, try one of the early Rickenbacker fives.
Oh, and if you want to sell it, let me know and I may be able to find a home for that poorly designed mistake-filled bass.
-bob