I love Gentoo. It's a great developer distribution. I've been using it since 2003 I think, and the current Gentoo install I use I have continually updated since 2012. When I get a new machine, I just copy the existing install over and build a new kernel.

Same, been using it since 2002, my current image has been rolling since 2008, that's when I switched to amd64. Never cared about the performance tuning aspect, it's all about flexibility and control.

Would Gentoo not be subject to the effects of dodgy upstream patches too?

Gentoo doesn't use systemd by default, it has its own init system called OpenRC that's kinda sorta like a framework for sysv. Despite being shell based, it's very fast, my system can get from GRUB to Firefox in less than ten seconds if you enable autologin and add Firefox to your.Xsession.

Gentoo maintains forks of udev and logind, imaginatively named eudev and elogind. I use eudev, but elogind is unnecessary for me because I don't use Gnome3. But if that's your thing I'm not stopping you.

Pulseaudio is easy to remove by virtue of Gentoo's source based package model. Dbus less so; many applications have a hard dependency on it.

I think it's possible to use a BSD kernel, but you will very likely deal with a lot of breakage.

Gentoo is just so much easier to administrate that other distros it's unreal.

Unless you are trying to run software that explicitly depends on some of the brokenness from upstream (Gnome3) you can just setup a classic system that will behave the same way you're used to and honestly, I didn't encounter problems with software in that configuration

Gentoo tends to maintain out of tree patches (possibly to remove upstream changes), or complete replacements (like eudev/elogind).