One big thing you should have pointed out in regards to BASE is how it utterly screws up on-page hash links. I was one a big advocate of it, but as using :target on the CSS side of things is more commonplace, that href="#something" gets DIRECTLY applied to BASE and not the current page's path makes it a pain.
... and as to the once deprecated but now magically back target attribute, which has made a return regardless of what UTTER USABILITY CRAP it is, just keep in mind most of the time you use it you've made an accessibility violation.
Don't shove new windows/tabs down the user's gullet where they likely don't want one. The user wants it in a new tab, they can middle-click or ctrl-click. TARGET is for frames, something that other than video or advertising plugins we as developers have ZERO business using in the first place.
Hence why it being allowed back into HTML 5 is as dumbass and stupid as EMBED, the creation of AUDIO and VIDEO tags separate from OBJECT (100% hurr durrz), or the mind-numbingly stupid -- and thankfully defunct -- HGROUP tag. All things which prove the folks at the WhatWG were unqualified to create HTML 4 Strict's successor, and basically wanted to drive development practices back to the worst of the mid to late '90's browser wars.