I like pimping my basses - but there has to be enough right with it in the first place.
For me the neck profile and the balance of the instrument is vital. No amount of reasonably priced pimping will sort out a neck that isn't comfy.
Balance can sometimes be pimped - If an otherwise comfortable bass is a bit neck heavy but has old fashioned tuners on it then a set of Hipshot Ultra-lites can cure the problem. On a 5 string bass with trad tuners (Fender, Sandberg, Musicman etc) a change to Ultra-lites can save 1/2 pound. And that 1/2 pound is all saved from the headstock. The difference can be amazing.
I'm about to do a pickup swap in my Stingray5. I love the feel of the bass and the neck profile, but I find the sound a bit too aggressive for my current needs.
But I'm not afraid to get the router out if it will make an already brilliant bass perfect!