Please do not merge servers.
To start, this would have no impact to BGs. All realms in Era already are pooled together in BGs. Era pools all realms together for BGs regardless of realm type or region or cluster (within North America as mentioned above).
Second, Blizzard already offers Free Character Moves to the designated primary clusters — Mankirk and Whitemane. Anyone who wishes to be in these servers is either already there or has a FCM to move there.
Related to the previous point, those of us not are Mankirk and Whitemane do not wish to play there. Grobbulus has about 50 people playing on alliance (we just got Kt down after 2 years of progression!). All of us have FCMs to join the main clusters but actively do not wish for this. In fact, we have grown in numbers mostly with people transferring, paid, from those clusters to Grobbulus.
Finally, pretend we did merge servers. You’re talking maybe 100 people total across all the other realms moving together. Is 100 extra people (who, mind you, already are pooled into your BG queues today) really going to make a difference? We’re already in the same BGs as you. And likely, many of those 100 players stop playing after being forced to move servers.