After 30+ years playing I own just a bunch of keeper basses nowadays. At my highest I used to own a dozen avg. Now I'm shrinking to 5 that have A REASON, a merit of their own each. I own a couple Sringray5s (my main bass since forever, 10 years in I bought a second specimen -both ceramic-). Those are keepers forever. After searching a skinny neck 5er that'd serve me well for occasional Fender like duties (minus the sketchyness of dealing with Fender) I've finally settled in with a Schecter CV-5 (sweet mid-budget instrument, looks, feels, plays and sounds not a cent cheaper than my Rays). Then I have this very cheap P-bass kit I got as a gift in early 2016 and has been a work in progress that eventually became a 5 string fretless reverse P+J that got me back to fretless (once my main gig) after 16 years (God bless LaBella LTFs!).
Now I'm looking into a Rockbass StarBass 5 to close the lineup (while selling an Epi Viola bass -unused for years-). I'm even contemplating buying a lefty and convert it as these are half the price (new or used, not much of a difference, you see them for 1000€ at stores, people sell them for 850€ used, no way I'm paying that much for a Chinese Rockbass, 1000€ is used German Corvette/Thumb BO range here).
I'm probably no more than a modest DIYer for Adam Carolla's standards (sw consulting pays the bills but I've usually been handy at manual labor and "educated" -can use many tools, basic woodworking, A/C, electrode welding, basic electronics, etc.-). I started skating longboards almost 10 years ago, around 35 (after really sucking on popsicles when 20 years before) and almost immediately I started
building my own decks and making some for friends and even selling some, went on to achieve great technically solid products.
I have all my instruments mostly stock. Now, I've always been familiar with guitar electronics, have installed preamps, pickups and other upgrades for people several times over the years and I've made some extra cash for years doing guitar/bass tech work. I'm neither educated nor brave enough to try too invasive mods on anything. Still, a few years ago I did the only mod I'd ever dare to my Ray 5ers, both have a switch that toggles between coils when used in the single+phantom coil position of the coil tap (center). It's only bridge-side coil stock, you can choose which on mine (it also reverses the phantom coil so it still cancels hum). This is a reversible mod (should just require some soldering and a pickguard replacement).
My kind of experience was enough to make the extensive modding process that took place in the red bass on the right (back then still fretted) pleasing and "safe" enough. Electronically it's simple too, VVT + S1 (series/parallel, the P volume is a push-pull). This is how it looks today...
I bought a "parts" Jazz for 38€ some months ago. Neck was useless and body was a miscut "homage" to a Jazz Bass (both soon to become wall hangers). BUT, all hardware and electronics were OK, so I've got a body and neck (50€ all from AliExpress) coming my way to make something pretty out of it (and probably donate it to somebody who really needs it). Also in the process of restoring a crappy (and also rather neglected) Kramer short scale/single PU guitar I got from my sister (after years of it wandering around her home).
So, in conclusion, I'm all for DIY... just ON THE CHEAP. Don't really dare do too serious/expensive stuff, either mod expensive gear or build from high quality parts. If I do the aforementioned StarBass conversion from lefty to right handed it'd be my most expensive and invasive mod of an instrument (at about 500€, even tho' it'd save me another 500€ I'd have to spend to have a right handed one).