After the re-balancing, it will be possible to instacast BI at full def with only 1 tower and using a "normal" endgame setup. The key is the 100 NanoInits given on Embrace. Sure, I'd prefer more, so towers wouldn't be needed and everyone had equal opportunities, but that doesn't seem to be the case atm. I'm personally counting on the re-itemization that will follow the re-balancing will add what's needed to even the playing field.
tldr; I'm positive we can insta cast BI @ full def after the re-balancing without sacrifices.