As player of Icecrown realm I appreciate the will and effort to make battleground queue shorter by enabling cross realm battlegrounds.
Unfortunately, aliance side still struggles to get the queue. from 8pm server time till 11pm we barely get into 2 battlegrounds 3 is the max if we are lucky.
So my suggestion is to implement mercenary mode for battlegrounds. Same thing blizzard implemented in legion expansion time and it is live since then.

https://www.youtube.com/watch?v=Nv3HK0Wyc4U