Would it make sense to exchange the pickups of a squier p-bass or would that be completely useless? The main reason for me to do this would be to get a better sound without having to buy a completely new bass. ( i'm always kinda short on money , thats why i bought a squier in the first place )
If it plays to your liking, then it may be worth it. Unplug the guitar, rest your hear on the upper horn and play it... does it sound good (full, deep, warm)? If so, some other pickups might do the trick. If it sounds thin and tinny, probably not. Active pickups may help in that case, but you cannot completely rely on them to compensate for lack of quality in the instrument itself. Sometimes you can get a Squire or other inexpensive guitar that is really quite nice for the price. They tend to be cheaper becuase it is a crap-shoot. You never know. Just keep in mind that beefing up that guitar could cost more than trading it in on a used one that sounds better already.
I put Seymour Duncan Quarter Pounders on my Squier P-Bass and I love the sound. The stock Squier pickups are WEAK. I really like the sound of it now. The pickup was really cheap too, about $60 USD. If you upgrade your pickup, I recommend something like the Qtr Pounder, or something else with a high output. You might have to drill new holes for it to fit. Mine wasn't quite right, but I just screwed it into the body wood without one problem.