1) Personally, I think the AI is a detriment to the round. Sure, there are very good AIs, such as Harmony, Arlo, APEX, Aboshehab. But, there are also many, MANY shitty ones. As an AI, you have to purposefully play "badly" to give antags leeway, to make a good round. I think that sucks for game design. So, making it not appear, or making it a "later in the round" thing, would alleviate that.
2) With the removal of the AI, there's a bit of a void in access and synthetic assistance. The addition of another borg fills that void, and makes the station feel a bit more autonomous. That's my personal opinion, and I don't feel very strongly about it, so any other good opinion will sway me.