I have done plenty of this but if you buy a good enough instrument to start, thereās no need, beyond perhaps personal preferences/trivial swaps like strap locks or tuning machines.
No desire at all to change anything on my BBās, and the only reason I changed the tuners on my SBV is that the design is so light it has a little dive with the stock ones (which are otherwise excellent). Everything else, especially the pickups, are fantastic on both.
Modding is platform dependent and not price point to me. @howard sent me a link for the Yamaha motion bass and I jumped on that. Itās a few hundred bucks but it requires no modification only string changes.
This is good advice for beginners too; buying a proven, high quality older bass used can be a way better plan than buying a new entry level model, and cost the same or less for a much, much better instrument.