It's only too late to start a build diary when you have finished. And in my case sometimes not even then. I "finished" the one that is my current avatar, but did not like the way it came out for a variety of reasons...and so after several years of having it finished I reopened the build diary, refinished, redid the neck, put on some new hardware...

As to the holes in the back... I haven't seen it with bridges, but I have seen it with other hardware. A lot of Danelectro pickups are adjusted from the back of the body. On one of my basses I have a some switches that I recessed on the back.

I made two of my basses string-through to help keep the bridge in place. A fender style bass because the body was paulownia which I thought might be too soft to hold the bridge well. I have since learned that may not be a problem... but I also did string-through on a Gibson style bass to put downward pressure on the posts.

With specific regard to the 3-point bass bridges, there are lots of references to them pulling out on Gibson and Epiphone forums...as well as on this forum. Gibson even issued some Ripper and Grabber basses using the 3-point as string-through.

Your solution looks good. I can't think of any good reason not to do it the way you did.